root/trunk/RELEASE_NOTES.txt @ 5047

================================================================
Logtalk - Open source object-oriented logic programming language
Release 2.37.2

Copyright (c) 1998-2009 Paulo Moura.        All Rights Reserved.
Logtalk is free software.  You can redistribute it and/or modify
it under the terms of the "Artistic License 2.0" as published by 
The Perl Foundation. Consult the "LICENSE.txt" file for details.
================================================================


RELEASE NOTES
=============


2.37.2 - June 29, 2009

    Added support for parsing reexport/2 module directives when compiling
    Prolog modules as Logtalk objects. The predicate renaming operator as/2
    found on SWI-Prolog and YAP is also supported.

    Added support for using grammar rule non-terminal indicators in the uses/2,
    multifile/1, reexport/2, and use_module/2 directives.

    Added support for parsing operator declarations in the module/2, export/1,
    reexport/2, and use_module/2 module directives.

    Added support for declaring and defining object and category multifile
    grammar rules.

    Fixed a bug where a failed load of a settings file could be reported as
    successful.

    Added missing dynamic directives in the definition of the pseudo-objects
    "debugger" and "user".

    Eliminated message-sending overheads when sending messages to the pseudo-
    object "user".

    Allow the "debugger" built-in object to play the role of both a class and
    a prototype when being specialized or extended.

    Added support for compiling module-qualified arguments in calls to Prolog
    database and reflection built-in predicates.

    Added support for using multiple info/1 directives per entity and multiple
    info/2 directives per predicate (useful when compiling modules as objects). 

    Added limited support for translating queries as initialization goals when
    compiling modules as objects (queries must be calls to locally defined
    predicates or to predicates referenced in use_module/2 directives).

    Optimized performance of meta-predicates whose meta-arguments are goals,
    not closures, when using static binding.

    Updated the SWI-Prolog config file in order to support the proprietary
    predicate directives format_predicate/2, noprofile/1, and volatile/1.

    Updated the SICStus Prolog, SWI-Prolog, and YAP config files in order to
    workaround broken meta-predicate declarations for the built-in predicates
    format/2-3 and in order to support the sloppy use of the ensure_loaded/1
    directive within modules, rewriting it to a use_module/1 directive.

    Updated the ECLiPSe, SWI-Prolog, and YAP config files in order to support
    parsing of reexport/1 module directives.

    Updated the YAP config file in order to support parsing of the use_module/1
    module directive.

    Updated the ECLiPSe config files in order to support parsing of comment/2,
    import/2, inline/2, and set_flag/3 proprietary directives.

    Updated the SICStus Prolog config files in order to support parsing of the
    load_foreign_resource/1 proprietary directive.

    Updated the B-Prolog config file in order to support the new foreach/3-4
    meta-predicates and the new table mode directive in B-Prolog 7.3. Added
    definition for the "prolog_version" read-only compiler flag.

    Updated the XSB config file in order to enable support for multifile
    directives (version 3.2 or later is required).

    Improved conversion guide for migrating Prolog module code to Logtalk.

    Improved documentation and examples of using the term and goal expansion
    mechanisms.

    The "lgt2*.sh" documentation shell scripts have been updated to ignore
    XML files that are not XML documenting files generated by the Logtalk
    compiler.


2.37.1 - June 2, 2009

    Added support for declaring and defining object and category multifile
    predicates. This new feature is primarily intended to facilitate migration
    of Prolog code to Logtalk and should be used with caution as multifile
    support is spotty among back-end Prolog compilers (easily leading to
    portability problems). Multifile predicates can be both static or dynamic.

    Added support for compiling clauses for module multifile predicates within
    objects and categories in order to provide better integration with CLP(FD)
    and similar constraint packages.

    Added support for parsing module/2 directives whose export list contains
    operator declarations.

    Improved Logtalk compiler error-checking of file-level op/3 directives.

    Updated the Logtalk compiler to try to detect calls to proprietary built-in
    meta-predicates not declared in the config files. Detection may fail due to
    the lack of standardization of meta-predicate specifications.

    Updated the Logtalk compiler to avoid unexpected compilation errors when
    querying predicate properties due to the lack of standardization of the
    Prolog predicate_property/2 built-in predicate.

    Improved runtime error-checking for meta-calls whose closure argument is
    either Object::Closure or Module:Closure.

    Corrected a Logtalk compiler bug where a redefinition of a proprietary
    built-in meta-predicate (declared in the config files) would be ignored.

    Corrected a bug in the implementation of the Logtalk <</2 control construct
    where a redefinition of a built-in predicate would be ignored.

    Corrected a Logtalk compiler bug where initialization/1 goals would be
    compiled as normal code instead of as debug code when compiling a source
    file in debug mode.

    Updated documentation support to include predicate alias information on
    the automatically generated XML documenting files. Updated the sample XSLT
    transformations to output alias information.

    Corrected a bug in the YAP config file that prevented setting the "unknown"
    flag to "error" and the "language" flag to "iso". Added declarations for
    the proprietary built-in meta-predicates call_residue_vars/2, ignore/1,
    depth_bound_call/2, setup_call_cleanup/3, and setup_call_catcher_cleanup/4.
    Removed declaration for the outdated meta-predicate on_cleanup/1. Added
    support for the thread_initialization/1 proprietary directive.

    Updated the B-Prolog config file with declarations for the proprietary
    built-in meta-predicates fd_minimize/2 and fd_maximize/2.

    Updated the GNU Prolog config file in order to recognize the foreign/1-2
    proprietary directives. Added declarations for the proprietary built-in
    meta-predicates fd_minimize/2 and fd_maximize/2.

    Updated the ECLiPSe config files with declarations for the proprietary
    built-in control constructs and meta-predicates ~/1, not/1, and (-?->)/1
    (the last one only for the non-ISO config files).

    Updated the SWI-Prolog config files with declarations for the proprietary
    meta-predicates setup_call_cleanup/3, setup_call_catcher_cleanup/4, when/2,
    and with_output_to/2. Added support for the thread_initialization/1
    proprietary directive. Improved parsing of use_module/1-2 directives.

    Added a dummy definition for the predicate '$lgt_logtalk_prolog_encoding'/3
    to the config files of all back-end Prolog compilers that don't support the
    encoding/1 directive.

    Added predicate sequence/3 to the library object "integer".

    Added predicates append/2 and msort/2 to the library object "list". Fixed
    some termination issues with the length/2 predicate on buggy input.

    Added aliases foldl/4, foldr/4, scanl/4, and scanr/4 to the library object
    "meta".

    Added an experimental "logtalk_select.sh" POSIX shell script for switching
    between installed Logtalk stable versions.

    Added a POSIX integration script, "xsb64lgt", for using Logtalk with the 
    single-threaded, 64 bits version of XSB.

    Added a note on a workaround for compatibility issues between GNU Prolog
    and the contributed XML parser library. Thanks to Nicolas Pelletier for
    the bug report.

    Added a new example, "securemp", illustrating the safety rules used by
    Logtalk in the compilation and execution of meta-predicates (as described
    on the "Secure Implementation of Meta-predicates" PADL'09 paper).

    Extended the "constraints" example for SWI-Prolog and YAP illustrating
    the definition of custom constraint propagators within objects.

    Added instructions on how to enable a source code browser when editing
    Logtalk source files with the Vim text editor (using the Taglist Vim
    plugin and Exuberant ctags).


2.37.0 - May 11, 2009

    Improved dynamic binding performance by making calls to the lookup caches
    call the cached methods instead of simply returning the corresponding
    callable terms, therefore no longer requiring a meta-call for executing
    the methods. For multi-threaded back-end Prolog compilers, the new caching
    mechanisms forces the lookup cache dynamic predicates to be declared
    thread shared instead of thread local.

    Improved performance of the built-in database methods retractall/1 and
    retract/1.

    Improved performance of user-defined object and category meta-predicates.

    Added support for meta-calls whose closure argument is ::Closure.

    Simplified compilation and improved performance of predicates that call
    local user meta-predicates.

    Corrected a bug where calls to local user meta-predicates would fail.
   
    Corrected a bug where local calls to user meta-predicates would not be
    visible to the built-in debugger.

    Improved Logtalk compiler error checking for accidental redefinition of
    control constructs.

    Improved Logtalk runtime error checking for message sending and "super"
    control constructs when the message is only bounded at runtime.

    Updated the exception terms thrown when sending messages to self in order
    to use the ::/1 control construct for the culprit goal instead of the ::/2
    control construct.

    Simplified message sending implementation by removing the seldom used
    control constructs that allowed sending the same message to a conjunction
    or disjunction of objects.

    Specify \+/1, call/1-N, and once/1 as built-in local meta-predicates. 

    Disallow using Logtalk and Prolog built-in meta-predicates as messages in
    order to avoid conflicting semantics with user-defined object and category
    meta-predicates. The Logtalk control constructs (,)/2, (;)/2, (->)/2, and
    !/0 may still be used as syntactic sugar when sending a set of messages to
    a single object.

    Updated the Logtalk compiler to ensure that calls to the built-in meta-
    predicate call/2-N within a category have the same semantics as other
    built-in meta-predicates whose meta-arguments are goals.

    Improved performance of the :/1 control construct when using dynamic
    binding by adding a predicate lookup caching mechanism.

    Added support for using the :/1 control construct with a non-instantiated
    argument at compile-time (handled using dynamic binding at runtime).

    Allow a variable clause body to be interpreted as a meta-call instead of
    an instantiation error. Although is not recommended to use a variable as
    a goal instead of using the call/1 built-in meta-predicate, this change
    allows for uniform handling of variables as goals in clause bodies. Thanks
    to Victor Noel for the bug report.

    Updated the ECLiPSe config files in order to support the non-standard 
    *->/2 (aka "soft cut") control construct. Thanks to Victor Noel for the
    bug report.

    Updated the Ciao config file in order to support the non-standard if/3
    (aka "soft cut") control construct.

    Updated the Qu-Prolog config file in order to enable support for multifile
    directives (version 8.9 or later is now required).

    Updated the Windows installer in order to ensure compatibility with the
    new CxProlog 0.97.3 version. Updated the CxProlog config file in order
    to set the "underscore_variables" compiler flag to "dont_care".

    The library object "varlist" is no longer derived from "list" as several
    of the "listp" predicates are not meaningful or cannot be used with the
    same modes. Added a new library protocol "varlistp". Corrected several
    bugs in the implementation of the library object "varlist" predicates.
    Thanks to Victor Noel for the bug report.

    Added meta-predicates scan_left/4, scan_right/4, map/6-8, and partition/6
    to the library object "meta". Optimized performance of the meta-predicates
    fold_left/4, fold_right/4, include/3, exclude/3, map/2-8, and partition/4.

    Added predicates partition/5, same_length/3, selectchk/3, and
    subsequence/3 to the library objects "difflist" and "list".

    Added predicates product/3 and selectchk/3 to the library object "set".

    Updated the "puzzle" constraint example for SWI-Prolog to avoid leaking
    "clpfd" predicates in query binding results. Thanks to Ulrich Neumerkel
    for reporting the problem.

    Corrected a bug in the "expansion" example that prevented some of the
    example queries from working.

    Simplified running the "poem" example.


2.36.0 - April 9, 2009

    Added support for overriding Logtalk default compiler flags (specified
    in the back-end Prolog compiler config files) using new settings files.
    Logtalk will load a "settings.lgt" file in the startup directory. If 
    this file is not found, Logtalk will load a "settings.lgt" file in the
    Logtalk user directory. Requires running Logtalk with a back-end Prolog
    compiler supporting access to environment variables. Loading of settings
    files from the Logtalk startup directory is only available when running
    on Windows for B-Prolog, Ciao, GNU Prolog, SWI-Prolog, XSB, and YAP.
    SICStus Prolog is incompatible with this new feature, requiring manual
    loading of settings files after startup. Consult the "configs/NOTES.txt"
    file for compatibility details for other Prolog compilers.

    Updated the "cplgtdirs.*" scripts to copy an existing "settings.lgt" file
    from the backup of the Logtalk user folder to the new Logtalk user folder.

    Updated the Logtalk compiler and runtime and all the config files to use
    the more standard call/N predicates instead of the call_with_args/N 
    predicates.

    Improved the XML documentation automatically generated for objects and
    categories by appending to the compilation mode all the active optional
    features and the "threaded" and "synchronized" properties. Improved the
    XML documentation automatically generated for synchronized predicates by
    appending the "synchronized" property to the predicate compilation mode.

    Improved error handling for the built-in predicates logtalk_load/2,
    logtalk_compile/2, current_logtalk_flag/2, and set_logtalk_flag/2
    when checking flag names and values.

    Improved Logtalk compiler error and warning reporting by printing,
    whenever possible, the range of lines where the problem was found
    instead of printing only the starting line.

    Added new object properties "complements", "context_switching_calls",
    "events", and "dynamic_declarations". Added new category property
    "events". These properties are defined whenever the corresponding
    compiler flags are set to "allow" at the time of entity compilation.

    Corrected a bug where some file-related entity properties would not
    be stored when using back-end Prolog compilers that don't support
    multifile predicates.

    Corrected a bug (introduced in version 2.35.0) in the compilation
    and processing of "super" calls for objects that both instantiate
    and specialize other objects.

    Corrected a bug (introduced in version 2.35.1) in the Logtalk compiler
    that prevented compilation of Prolog modules as objects.

    Corrected a bug in the implementation of the Logtalk built-in predicate
    threaded/1 that would result in wasting space in the main thread message
    queue with duplicated messages. Thanks to Rui Marques for the bug report.

    Corrected a bug where the Logtalk compiler would report the number of
    compilation warnings with the "report" compiler flag set to "off".

    Updated the Logtalk compiler in order to avoid unwanted backtracking
    during source file compilation and when calling the entity creation
    built-in predicates.

    The compiler flags "context_switching_calls", "startup_message", and
    "altdirs" are no longer read-only flags in order to support changing
    their default values from within "settings.lgt" files. The possible
    values for the compiler flags "dynamic_declarations", "complements",
    "context_switching_calls", and "events" are now "allow" and "deny".
    Added a new read-only compiler flag "prolog_version". Renamed the 
    compiler flag "prolog" to "prolog_dialect".

    Changed object compilation in order to restrict the use of the <</2
    control construct to objects compiled with the "context_switching_calls"
    compiler flag set to "allow".

    Changed the "cplgtdirs.*" and installation scripts to no longer make a
    copy of the "configs" directory in the Logtalk user directory. Updated
    the customization instructions to advise users to edit the "settings.lgt"
    file instead of editing the Prolog configuration files.

    Changed the Windows installer script in order to create Logtalk startup
    scripts that start from the current directory as returned by the "%CD%"
    dynamic environment variable. This allows a shortcut to be simply copied
    to a Logtalk project directory without requiring editing its properties
    in order to set the startup directory to the project directory.

    Updated the XSB-MT integration scripts to make all lookup cache dynamic
    predicates thread private. Updated the XSB config file for version 3.2,
    which is now required for running Logtalk.

    Added a new '$lgt_prolog_feature'/2 predicate to all config files, used 
    for representing back-end Prolog supported features that are previously 
    represented by read-only compiler flags.

    Added new '$lgt_environment_variable'/2, '$lgt_startup_directory'/1, and
    '$lgt_user_directory'/1 predicates to all config files.

    Changed the default value for the "startup_message" compiler flag to the
    less verbose "flags(compact)".

    Updated the config files of the Ciao, CxProlog, GNU Prolog, ECLiPSE, and
    XSB compilers to set the default directory for temporary files depending
    on the host operating-system.

    Updated the config files of the Ciao, ECLiPSe, GNU Prolog, Qu-Prolog, 
    and SICStus Prolog compilers to return term position line numbers for
    reporting warnings and errors.

    Switched off use of multifile/1 directives for Amzi! Prolog due to its 
    buggy implementation on this Prolog compiler.

    Updated the Ciao config file to workaround a weird bug in the read_term/3
    predicate that prevented compilation of some Logtalk source files.

    Updated the K-Prolog config files in order to make the definition of the
    '$lgt_delete_file'/1 predicate compatible with Windows systems.

    Updated the predicate comments in the library protocol "loopp" in order
    to workaround the limitation on the maximum size of atoms in Qu-Prolog.

    Removed the obsolete SWI-Prolog hook file "swi_set_logtalk_context.pl"
    (the Logtalk control construct <</2 provides similar functionality).

    Added a check/1 predicate to all objects in the "types" library. This 
    predicate differs from the existing valid/1 predicate by throwing an
    exception when the argument is not valid instead of failing.

    Added multifile and dynamic declarations for the logtalk_library_path/2
    Logtalk predicate to the "libpaths/libpaths.pl" file. This change allows
    use of Ciao as the back-end Prolog compiler without patching the Logtalk
    compiler and runtime (but also results in a harmless warning when using
    GNU Prolog).

    Updated the POSIX integration scripts to export the environment variable
    LOGTALK_STARTUP_DIRECTORY before starting Logtalk.

    Changed the SWI-Prolog POSIX integration script to use the option "-s"
    instead of the option "-f" in order to allow loading of any existing
    user initialization file (".plrc" on POSIX systems; see the SWI-Prolog
    reference manual) before loading the Logtalk files. On Windows the use
    of the "-s" results in a weird double initialization bug.

    Workaround a compilation error in the object "salt/3" in the "searching"
    example when using SICStus Prolog as a back-end compiler.


2.35.1 - March 1, 2009

    Allow explicitly qualified module calls in the body of category and object 
    predicate clauses without requiring the calls to be wrapped within a {}/1
    control construct to ensure successful compilation. This requires an hack
    in the config files of most back-end Prolog compilers with module systems
    as the implementations of the predicate_property/2 built-in predicate 
    cannot be used to test if :/2 is a built-in control construct. Updated the
    config files of Amzi! Prolog, Ciao, IF/Prolog, Quintus Prolog, SICStus 
    Prolog, SWI-Prolog, XSB, and YAP.

    Improved the Logtalk compiler compatibility with Prolog meta_predicate/1
    directives that use the integer zero as an alternative to the atom ':' for
    denoting meta-arguments that are goals.

    Added limited support for calling Prolog meta-predicates defined in module
    libraries (meta-arguments must be goals, not closures; the Logtalk compiler
    assumes that an imported_from/1 property is defined for these predicates).

    Implemented a "warnings" value for the "report" compiler option, providing
    a less verbose compilation reporting where only warnings are printed.

    Corrected a Logtalk compiler bug where warnings related to synchronized
    predicates would be reported even with the "report" flag set to "off".

    Added support to the message sending mechanisms for using the object proxy
    access notation when the message receiver is only known at runtime.

    Changed the semantics of the Logtalk notation for accessing object proxies
    when sending a message to allow backtracking over the proxy goal.

    Updated the Logtalk compiler to avoid reporting multiples reference to the
    same unknown parametric object.

    Corrected a bug in the implementation of the "smart_compilation" compiler
    flag that would result in a misleading successful compilation of a source
    file containing syntax errors after the first failed compilation when the 
    errors are not corrected between compilations. Thanks to Joerg Schuster 
    for the bug report.

    Added a '$lgt_delete_file'/1 predicate to all config files. For back-end
    Prolog compilers that don't support a built-in predicate for deleting 
    files, the '$lgt_delete_file'/1 predicate simply fails. This predicate is
    used by the Logtalk compiler to ensure correct behavior of the compiler
    flag "smart_compilation".

    Updated the YAP config file to ensure that the "syntax_errors" proprietary
    flag is set to "error".

    Integration with GNU Prolog now requires version 1.3.1 or later of this
    compiler.

    Added a workaround to the ECLiPSE config files in order to support smart 
    compilation of source files (due to the non-standard implementation of the
    read_term/3 predicate that fails for syntax errors instead of throwing an
    exception).

    Updated the library object "term", adding a singletons/2 predicate and
    renaming the predicate vars/2 to variables/2 (the old name is still
    available but shall be considered deprecated). Both the variables/2 and
    the singletons/2 predicates return variables ordered as found when doing
    a depth-first, left-to-right term traversal. Optimized the implementation
    of the predicates ground/1 and variables/2 to use the Prolog built-in 
    versions of these predicates when available.

    Moved the Prolog Integration and Migration Guide into the User Manual.

    Updated the "BIBLIOGRAPHY.bib" file with recent Logtalk publications.

    Updated the "build_release.sh" POSIX shell script steps for building the
    MacOS X installer.

    Updated the Windows installer to disable by default the installation of
    the integration shortcuts for Ciao Prolog and Quintus Prolog as these 
    compilers require patches that render Logtalk incompatible with the other
    compilers.

    Simplified loading and testing instructions for the XML parser included
    in the "contributions" directory. Added a missing logtalk_library_path/2
    entry for XML parser directory.


2.35.0 - January 16, 2009

    Improved compilation of source code resulting in smaller intermediate
    Prolog files and better performance for most back-end Prolog compilers.

    Improved caching of message sending predicate lookups (by generating
    more reusable cache entries for public predicates, improving lookup
    performance and cache hits).

    Improved caching of ^^/1 calls (by generating more reusable cache entries,
    improving lookup performance and cache hits).

    Simplified compilation of meta-predicates. Allow meta-predicates to be
    specialized and called using the ^^/1 control construct.

    Simplified and improved performance of the multi-threading built-in
    predicates within the context of the pseudo-object "user" (e.g. for
    top-level queries).

    Changed compilation of once/1 goals in debug mode in order to make them
    explicit when tracing using the built-in debugger.

    Added support for multiple source-level and entity-level initialization/1
    directives (matching the ISO Prolog standard and current Prolog practice).

    Corrected a bug in the compilation of top-level queries for the Logtalk
    built-in predicates.

    Corrected a predicate scope checking bug when using the dynamic-binding
    cache entries.

    Corrected a bug when compiling entities in debug mode that contain
    initialization goals. Thanks to Parker Jones for the bug report.

    Corrected a bug in the library object "meta" where the deprecated
    predicates filter/3 and succeeds/2 are declared (using aliases) but
    not defined.

    Changed the formulas used for calculating sample skewness and sample
    kurtosis to match the formulas used in statistical software such as R.

    Added declaration for the proprietary findall/4 meta-predicate to the
    SWI-Prolog and YAP config files.

    Corrected processing of the proprietary load_foreign_files/3 directive
    in the YAP config file.

    Switched off use of multifile/1 directives for Ciao due to its buggy
    implementation on this Prolog compiler.


2.34.1 - December 15, 2008

    Allow the ^^/1 control construct to be used for calling any inherited
    predicate instead of being restricted to calling inherited predicates
    in the context of their redefinitions.

    Updated the Logtalk compiler to detect (and report as an error) the
    definition of two entities with the same name in a source file.

    Updated the Logtalk compiler to detect (and report as an error) any
    invalid relation between an entity and itself. In most cases, these
    errors could result in predicate lookup endless loops.

    Corrected a long-standing bug in the implementation of the Obj<<Pred
    control construct, which failed to properly set the execution context
    to the receiving object for top-level queries. This bug, which results
    in a stack overflow error, was uncovered by an unrelated bug fix in the
    previous Logtalk version.

    Fixed some broken links in the Logtalk XHTML documentation. Updated the
    screen CSS file to match the new, lighter style of the Logtalk website.

    Updated the "testing" example to take into account the recently added
    "dynamic_declarations" compiler flag.

    Added a set of double-clickable *.command Terminal.app files for starting
    Logtalk with selected back-end Prolog compilers on MacOS X.

    Updated the MacOS X installer postflight script to open the Logtalk
    installation folder, the *.command files folder, and the "README.txt"
    file.

    Updated the "BIBLIOGRAPHY.bib" file with recent Logtalk publications.


2.34.0 - November 26, 2008

    Added conditional compilation support, as found in some Prolog compilers,
    using the new directives if/1, elif/1, else/0, and endif/0. The arguments
    of the if/1 and elif/1 directives are subjected to goal expansion.

    Added a "prolog" read-only compiler flag whose value is the name of the
    back-end Prolog compiler (an atom). This flag is defined in the config
    files and can be used for conditional compilation of Prolog specific code.

    Added an expand_goal/2 built-in method to support explicit calls to the
    goal_expansion/2 user-defined hook. Updated the term expansion mechanism
    to allow the expansion to be a single term instead of a list of terms.
    Improved the documentation of the term and goal expansion predicates.

    Simplified the implementation of the threaded/1 built-in predicate.

    Removed support for the deprecated message_queue_create/1 Prolog built-in
    predicate.

    Corrected a bug in the implementation of the predicate_property/2 built-in
    method which would return wrong meta-predicate templates for predicate
    aliases. 

    Corrected a bug in the compilation of meta-calls to predicates defined
    in the pseudo-object "user".

    Corrected a bug that prevented goal expansion of source file initialization
    goals (expressed using the initialization/1 directive).

    Modified the "statistics" library to use the variance numerically stable
    algorithm to calculate accurate values for the standard deviation for both
    samples and populations. Thanks to Parker Jones for the bug report. Added
    calculation of sample and population kurtosis.

    Added predicates included/3, excluded/3, fold_left/4, and fold_right/4
    to the library entities "metap" and "meta" (requested by Paul Crocker).
    Renamed the predicates filter/3 and succeeds/2 to included/3 and map/2,
    respectively (the older names are still available using aliases defined
    in "meta").

    Changed the file name extension of all config "*.config" files to "*.pl".
    Changed the file name extension of all library "*.notes" files to "*.txt".

    Updated the "metapredicates" example with Paul Crocker's contributions
    to illustrate the use of some of the meta-predicates implemented in the
    Logtalk library.

    Updated the "expansion" example to illustrate the new expand_goal/2
    built-in method. Improved example documentation.

    Added an example, "cc", of using conditional compilation directives to
    implement a portable operating-system interface for selected back-end
    Prolog compilers.

    Added an example, "prototypes", illustrating the concept of "prototype".

    Added syntax coloring support for the new expand_goal/2 method and for
    the if/1, elif/1, else/0, endif/0, set_logtalk_flag/2, ensure_loaded/1,
    and set_prolog_flag/2 directives to the supported text editors and
    syntax highlighters.

    Fixed a block comment syntax coloring bug in the support for the Highlight
    syntax highlighter with the help of André Simon.


2.33.2 - November 3, 2008

    Added support for using the set_logtalk_flag/2 directive in source files.
    This directive is executed when read (thus affecting the compilation
    of the source code that follows) but its scope is restricted to the source
    file being compiled.

    Allow a complementing category to define aliases for predicates of the
    complemented object.

    Improved reporting of line numbers for syntax warnings and errors when 
    using YAP or SWI-Prolog as back-end compilers (requires YAP git version).

    Improved reporting of entity existence errors for top-level queries.

    Implemented a more flexible internal representation of entity properties.
    Added entity properties file(File, Path) and lines(Start, End) for 
    entities compiled and loaded from source files. The property lines/2 is 
    only available when using YAP or SWI-Prolog as back-end compilers.

    Added missing "built_in" properties for the built-in protocols "expanding"
    and "monitoring".

    Corrected a bug where compiler options are not cleared after compilation
    of source files. This bug would result in wrong compilation of messages 
    sent from the top-level interpreter (i.e. messages sent by the pseudo-
    object "user") whenever events or hooks compiler options are used.

    Updated the Logtalk compiler to print a warning when defining clauses for
    the built-in predicates term_expansion/2 and goal_expansion/2 without a
    reference to the built-in protocol "expanding".

    Updated the Logtalk compiler to provide file information when printing
    redefined entity warnings if the files of the new and the old definitions
    are different (requires support for the file/2 entity property).

    Updated the Logtalk compiler to prefix all informative messages with the
    line comment character, "%", to make it easier to use interactive section
    transcripts as scripts.

    Corrected a bug that prevented using synchronized/1 predicate directives
    within protocols.

    Corrected a bug where portability warnings would be reported even when the
    "report" compiler option is turned off. Corrected a bug where portability
    warnings would not increment the warnings counter.

    Added an optimization and safety compiler option, "complements", that 
    allows objects to be compiled with support for complementing categories 
    either enabled or disabled. The default value (set in the config files)
    is "off" (disabled).

    Added an optimization and safety compiler option, "dynamic_declarations",
    that allows objects to be compiled with support for dynamic declaration of
    predicates (using the built-in database methods asserta/1 and assertz/1) 
    either enabled or disabled. The default value (set in the config files) is
    "off" (disabled).

    Updated the Logtalk built-in debugger to print goal invocation numbers 
    and to accept the return and enter keys as alternatives to the "c" key
    ("creep") when tracing. Updated the implementation of the "display"
    command to include the write options quoted(false) and numbervars(false)
    (as common in most Prolog debuggers). Added a "unify" command.

    Modified the implementation of the built-in predicate define_events/5 to
    throw an exception when the monitor object doesn't define the required
    event handler methods (previously the define_events/5 call would simply
    fail).

    Added a customized version of the read_term/2 predicate to all config 
    files that returns the line where a term starts for back-end Prolog 
    compilers whose implementation of the read_term/2 predicate supports 
    this information.

    Updated the shortcut created by the Windows installer for integration with
    K-Prolog to require version 6.0.4 of this compiler.

    Updated the User Manual comparison between Logtalk nomenclature and C++
    and Java nomenclatures.

    Added a simple example, "instvars", illustrating how to define instance
    variables, default variable values, and setter and getter methods.

    Added a simple example, "classmethods", illustrating how to define 
    "class methods" as found on class-based object-oriented programming
    languages.

    Improved the documentation of the "complements", "hello_world", "hooks",
    and "msglog" examples.

    Added a new logic puzzle programming example, adapted with permission 
    from Kevin Stone's BrainBashers website (http://www.brainbashers.com/).

    Updated all the examples that make use of event-driven programming
    ("birthdays", "bricks", "complements", "msglog", "polygons", "profiling",
    and "searching") to ensure correct functionality after fixing the bug in
    cleaning compiler options after compilation of source files.

    Updated the "dynpred" example to use the new "dynamic_declarations" 
    compiler option. Updated the "complements" example to use the new 
    "complements" compiler option. 

    Corrected a Vim syntax coloring bug with line comments occurring within
    entity opening directives.


2.33.1 - October 12, 2008

    Added a syntax construct for easy access to parametric object proxies
    represented as Prolog facts when sending a message ({Proxy}::Message).
    Updated the "proxies" example to illustrate this new functionality.

    Improved the Logtalk built-in debugger to print clause numbers for 
    static predicates at the unification ports ("fact" and "rule").

    Modified the built-in methods create_category/4, create_object/4 and
    create_protocol/3 to accept a variable as the first argument, which 
    will be instantiated to the identifier generated for the new entity.

    Modified the database built-in methods to allow initialization of static
    predicates for dynamic objects when the predicates are declared in "this".
    These changes simplify the initialization of dynamic objects when writing
    constructors. The dynamic objects must be descendants of "this".

    Fixed a bug in the Logtalk compiler that would result in failure to 
    restore the operator table in case of compilation error.

    Removed support for the deprecated mutex_create/1 Prolog built-in 
    predicate.

    Updated the XSB config file by switching off the use of multifile/1 
    directives when compiling Logtalk source files as a workaround for know 
    bugs in the implementation of this directive for dynamic predicates.

    Updated the ECLiPSe 6.0 config files in order to switch on the use of 
    multifile/1 directives.

    Update the CxProlog config file to work with and require version 0.97.2.

    Updated the Windows installer to warn the user when it fails to detect 
    the installation of the selected Prolog compilers. Fixed a bug where the
    creation of the K-Prolog integration shortcut could fail when performing
    a custom installation. Fixed a bug in detecting a CxProlog installation.

    Added a library for descriptive statistics. For details, see the file 
    "library/statistics.notes".

    Added a new library object, "pairs", defining predicates over lists of 
    pairs (key-value terms).

    Added a new library object, "gensym", defining predicates for generating
    unique atoms (object protocol based on the "gensym" module of SWI-Prolog).

    Added a predicate partition/4 to the library entities "metap" and "meta".

    Added predicates plus/3 and succ/2 to the library object "integer".

    Added predicates is_ascii/1, is_white_space/1, is_quote/1, is_period/1,
    is_punctation/1, and parenthesis/2 to the library entities "characterp"
    and "character".

    Modified the implementation of the predicate product/2 in the library 
    object "numberlist" to fail for empty lists.

    Added an example, "people", illustrating a simple implementation solution
    for object constructors.

    Improved "metainterpreters" example.

    Improved performance of the object initialization and release predicates
    defined in the category "initialization" of the "roots" example.


2.33.0 - September 1, 2008

    Applied several optimizations to the Logtalk compiler, mostly related to 
    non-detected deterministic predicates due to calls to dynamic predicates 
    or due to limitations in clause indexing by most Prolog compilers.

    Added support for using Prolog use_module/2 directives in objects and 
    categories. This allows module predicates to be called using implicit 
    qualification, improving readability. The use_module/2 directive supports
    the declaration of predicate aliases using the notation Original:Alias.

    Added support for meta-calls whose closure arguments are explicitly 
    qualified (using either Object::Closure or Module:Closure).

    Added support for using the ensure_loaded/1 and the set_prolog_flag/2 
    directives in source files. These directives are both processed when 
    read (thus affecting the compilation of the source code that follows) 
    and copied to the generated intermediate Prolog files.

    Corrected a set of singleton variable related bugs in the Logtalk compiler
    and runtime. Thanks to Joachim Schimpf and Kish Shen work on the improved 
    singleton variable checking code found on the new ECLiPSe 6.0 compiler.

    Simplified the implementation of the Logtalk built-in debugger. Changed 
    the implementation of the debugger abort command to use the de-facto 
    standard Prolog built-in predicate abort/0. Corrected a bug that prevented
    the use of the command "ignore" at the redo port.

    Removed the Logtalk dispatcher thread used for dispatching asynchronous 
    multi-threading calls, simplifying the implementation and improving the 
    performance of the asynchronous built-in multi-threading predicates.

    Corrected a bug in the implementation of the threaded_once/1-2 built-in 
    multi-threading predicates (use of detached threads could make the methods 
    fail despite the success of the thread goals).

    Improved performance of multi-threading applications (specially on MacOS X)
    when using SWI-Prolog as the back-end compiler by making the lookup caches 
    thread local.

    Small performance improvement of the threaded/1 built-in multi-threading 
    predicate.

    Added a multifile/1 directive for the logtalk_library_path/2 predicate.

    Corrected a bug in the verification of portable calls that would fail to 
    flag the soft-cut control construct (_ *-> _; _) found on some Prolog 
    compilers.

    Corrected a bug in the implementation of the built-in database predicates 
    retract/1 and retractall/1 when adding a cache entry for a local dynamic 
    predicate with no scope declaration.

    Corrected a bug in the compilation of source file op/3 directives whose 
    third argument is a list of operator specifiers instead of a single 
    operator specifier.

    Added ECLiPSe 6.0 config files. Modified the POSIX script "eclipselgt" 
    to test for both ECLiPSe 5.10 and 6.0 versions. Added Windows shortcut 
    to start Logtalk with ECLiPSe 6.0.

    Updated the GNU Prolog config file to allow Logtalk to recognize as 
    built-in predicates the finite domain solver built-in predicates.

    Added a new set of examples, "constraints", illustrating how to use the 
    Constraint Domain Solver libraries available with B-Prolog, ECLiPSe, 
    GNU Prolog, SWI-Prolog, and YAP. Thanks to Markus Triska for his help 
    with the YAP and SWI-Prolog CLP(FD) examples.

    Updated the "mtbatch" example to provide multi-threading overhead data
    for the competitive or-parallelism benchmark.


2.32.2 - July 26, 2008

    Simplified the predicate lookup linking clauses that are generated when 
    compiling private and protected entity relations, resulting in a small 
    runtime performance improvement when looking up non-cached predicate 
    declarations.

    Simplified and optimized handling of predicate aliases when looking up 
    predicate declarations and predicate definitions.

    When sending a message to an object using the ::/2 control construct, 
    also check if the sender matches the scope container when the message 
    does not correspond to a public predicate. This is necessary in order 
    to allow calling a protected or a private predicate in "this" from 
    within a category.

    Updated the Logtalk compiler to throw an error when detecting a call 
    to a dynamic predicate in the body of a predicate clause defined in a 
    category.

    Optimized the implementation of the ^^/1 control construct. The Logtalk 
    compiler now requires an instantiated, callable argument that must have 
    the same functor and arity of the predicate being (re)defined.

    Allow the ^^/1 control construct to be used within extended categories.
    Updated the "engines" example to illustrate this new functionality.

    Moved support for categories that complement existing objects from the 
    code generated when compiling objects to the Logtalk runtime, making the 
    implementation of this feature easier to maintain and contributing to 
    smaller code sizes of the intermediate Prolog files.

    Corrected a typo in the exception term throw by the built-in database 
    method assertz/1 when an error occurs while trying to assert a fact.

    Restored the redefined entity warnings for back-end Prolog compilers 
    that support multifile predicates (broken in the final version of 2.32.1).

    Changed the format of the Logtalk compiler informative messages for 
    better readability.

    Improved simplification of the clauses generated by the compilation of 
    object and category predicate clauses.

    Corrected a bug that prevented asserting and retracting clauses in "this" 
    from within a category.

    Corrected a bug in the implementation of the built-in database method 
    retractall/1 when retracting clauses in an object compiled in debug mode.
    Thanks to Parker Jones for the bug report.

    Updated all config files due to changes to the predicate used to declare 
    proprietary meta-predicates, '$lgt_pl_meta_predicate'/1. Added a second 
    argument to represent if the meta-predicate is either a built-in predicate 
    or a built-in control construct. This is necessary in order to properly 
    compile calls to these proprietary meta-predicates when in debug mode.
    Thanks to Victor Noel for the bug report.

    Corrected a bug in the config files hooks used in handling proprietary 
    Prolog directives for the SWI-Prolog, B-Prolog YAP, SICStus, and XSB 
    Prolog compilers. Added a new internal predicate for constructing 
    predicate indicators for compiled entity predicates that simplifies the 
    config files hooks used in handling proprietary Prolog directives.

    Changed the valid values of the read-only compiler flag "break_predicate"
    to "supported" and "unsupported" for consistency with other read-only 
    compiler flags.

    Updated the SWI-Prolog config file to set the Prolog flag "optimise" to 
    true. Added declaration for the setup_and_call_cleanup/3 meta-predicate.
    Removed setting of the deprecated "prompt_alternatives_no_bindings" 
    Prolog flag. Oldest SWI-Prolog compatible version is now 5.6.44.

    Updated the GNU-Prolog config file, adding a declaration for the 
    call_det/2 proprietary meta-predicate. GNU-Prolog version 1.3.0 or 
    later is now required.

    Added list mapping predicates map/4 and map/5 to the "metap" library 
    protocol and the "meta" library object.

    Added a proper definition for the predicate select/3 to the "varlist" 
    library object.

    Added a new example, "logging", of using a category to define a set of 
    predicates that handle a dynamic predicate in the context of "this" 
    (i.e. in the context of the objects importing the category).

    Added a new multi-threading example, "integration2d", implementing methods
    for numerical integration for functions of two variables, contributed by 
    Paul Crocker.

    Updated the "integration" multi-threading example by bringing all example 
    functions under the same object in order to allow for static binding. This
    is essential for good results in operating-systems with poor mutex thread 
    synchronization performance such as MacOS X.

    Added experimental support for the GeSHi syntax highlighter, contributed 
    by Clara Dimene.

    Improved support for the Pygments syntax highlighter, correcting coloring 
    bugs when there are single line comments in the same lines of an opening 
    entity directive.


2.32.1 - July 7, 2008

    Restored the redefined entity warnings for back-end Prolog compilers 
    that support multifile predicates. Simplified updating of the runtime 
    tables when compiling and loading source files with back-end Prolog 
    compilers that don't support multifile predicates.

    Changed the representation of the runtime tables for loaded entities 
    in order to drop the need of a "functors clause" per entity. This avoids 
    some redundancy on the representation of entity functors and also helps 
    reducing a bit the size of the generated Prolog files.

    When reloading an object, also clean all entries in the event handlers 
    table where the object plays the role of a monitor.

    Modified the Logtalk runtime to clean all lookup caches when compiling 
    and loading source files (instead of doing it only when the files 
    redefine existing entities).

    Corrected a bug that prevented using predicate aliases with the :/1 
    control construct without static binding.

    Updated the CxProlog config file to take advantage and require the new 
    0.97.1 version (which implements some more ISO Prolog predicates and 
    expands support for text encodings).

    Updated the B-Prolog config file to take advantage and require the new 
    7.1 version (which adds support for the multifile/1 predicate directive).

    Updated the SWI-Prolog config file notes about possible compatibility 
    issues with the default setting of the proprietary "iso" Prolog flag 
    to "true".

    Updated the SWI-Prolog hook file, "swihook.pl", to avoid hijacking the 
    arguments of use_module/1-2 calls (which resulted in wrongly loading 
    Logtalk libraries with the same name as the SWI-Prolog library modules 
    we intended to load).

    Updated the "k6.config" config file for the K-Prolog 6.0.3 release.
    Renamed the K-Prolog 5.1.x config file from "k.config" to "k5.config" 
    to avoid being mistaken for the K-Prolog 6.0.x config file. Updated 
    the "plclgt.sh" integration script to work with both K-Prolog 5.1.x 
    and 6.0.x versions.

    Renamed the SICStus Prolog 3 config file from "sicstus.config" to 
    "sicstus3.config" to avoid being mistaken for the SICStus Prolog 4 
    config file.

    Updated the POSIX integration scripts and the Windows installer script 
    to detect outdated versions of the Logtalk user folder (setting the 
    compatibility version to 2.32.0 or later).

    Improved the Prolog migration guide on converting code that makes use 
    of multifile predicates.

    Added note on licensing conditions to several files. Clarified copyright 
    and license conditions for files on the "contributions" folder. Clarified 
    dual-licensing conditions for text editor and syntax highlighter 
    supporting files. Added license file to the TextMate bundle.

    Updated support for the Vim text editor (changed the Logtalk file type 
    plug-in to set the path to the completion dictionary and updated the 
    installation instructions).

    Updated the support for the Pygments syntax highlighter to avoid marking 
    as errors non-standard directives.


2.32.0 - June 16, 2008

    Updated the Logtalk compiler and runtime to use multifile predicates for 
    the runtime tables of loaded entities and entities relations. This is 
    necessary to generate sensible intermediate Prolog code for large files 
    with tens of thousands of objects. The workaround of using the directive 
    initialization/1 is still available (for now) for Prolog compilers that 
    fail to support the thirteen years old ISO Prolog standard.

    Updated the Logtalk runtime error handler to test for non-instantiated 
    exception terms. Thanks to Joerg Schuster for the bug report.

    Corrected two bugs in the implementation of the built-in meta-predicate 
    threaded/1 when canceling individual threads. The first bug resulted from 
    out-of-order thread status messages. The second bug resulted from a leak 
    of thread results between calls to the threaded/1 predicate. Changed the 
    thread cancellation process to not automatically releasing any locks, 
    leaving that task to a catcher associated to the thread goal.

    Added a new default compiler option, multifile_directive, to all config 
    files. Possible values are "supported" and "unsupported".

    Added instructions on how to patch the Logtalk compiler in order to use 
    Quintus Prolog as the back-end compiler.

    Removed from the YAP POSIX integration script the command-line options 
    setting the initial stack, heap, and tail data area sizes. These settings
    are no longer necessary for recent YAP versions.

    Updated the Windows installer script to search the registry for the 
    location of the YAP installation (for YAP 5.1.3 or later versions).

    Added missing implementation of the predicate as_dictionary/2 to the 
    "bintree" library object. Thanks to Victor Noel for the bug report.

    Updated all the search methods in the "searching" example to delegate 
    checking for cycles to the state space being searched (thus allowing 
    state descriptions to carry additional information that should not be 
    taken into account when comparing states). Updated the "salt" example 
    to support heuristics.

    Updated the "mtbatch" example to include a benchmark test for competitive 
    or-parallelism applied to state-space search (using the resources from the
    "searching" example). Improved the example documentation.

    Added a filetype plugin for the Vim text editor. Updated the installation 
    instructions. Updated the syntax coloring support to properly highlight 
    quoted atoms and strings in the opening directive of parametric objects. 
    Fixed an auto-indentation bug when opening and closing a conditional 
    block in a single line in the last goal a predicate clause body. Thanks 
    to Victor Noel for the bug report.

    Corrected missing installation of the "VERSION.txt" file when building 
    Linux RPMs.


2.31.6 - May 26, 2008

    Fixed a Logtalk runtime bug when using the :/1 control construct to 
    call a predicate defined in a category extended by a category that 
    is imported by the object making the call.

    Fixed a Logtalk compiler bug when compiling an alias/3 predicate 
    directive within a category that extends other categories.

    Fixed a Logtalk compiler bug when compiling a class that imports a  
    category that extends other categories. Thanks to Victor Noel for 
    the bug report.

    Small performance improvement to the caching of category predicates 
    when using static binding.

    Removed from the YAP config file the definition of the forall/2 
    predicate, which have been added as a built-in predicate in YAP 
    version 5.1.3 (the current YAP CVS version must be used; the last 
    stable version, 5.1.2, is broken on Windows). Added support for 
    the proprietary if/1, else/0, elif/1, and endif/0 directives (when 
    used outside Logtalk entities).

    Updated the SWI-Prolog config file with support for the proprietary 
    if/1, else/0, elif/1, and endif/0 directives (when used outside 
    Logtalk entities).

    Improved the "complements" example, moving the category initialization 
    goal to the beginning of the example source file.

    Added support for the Pygments syntax highlighter (co-developed with 
    Clara Dimene).

    Added a new sample Logtalk source file for testing syntax coloring 
    support.

    Added missing auto-completion keywords for the ISO Prolog standard 
    arithmetic functions to the SubEthaEdit, TextMate, Notepad++, jEdit, 
    Vim, and Smultron text editors.

    Corrected a bug in the SubEthaEdit syntax coloring support for the 
    imports_category/2-3 built-in predicate. Added some missing files 
    (license and mode settings) to the SubEthaEdit mode bundle.

    Corrected a bug in the Vim syntax coloring support for the ISO Prolog 
    built-in predicate current_char_conversion/2 and added missing support 
    for for quoted atom escape sequences.

    Corrected a bug in the jEdit syntax coloring support for hexadecimal 
    numbers and added missing support for the extends_category/2-3 and 
    at_end_of_stream/0 built-in predicates.

    Added missing support for the syntax coloring of the external call 
    Logtalk control construct, {}/1, to the Highlight package. Corrected 
    a bug with 0'Char constants and with octal and hexadecimal escape 
    sequences.

    Added missing support for the syntax coloring of the external call 
    Logtalk control construct, {}/1, and for quoted atom escape sequences 
    to the TextMate text editor.

    Added missing support for the syntax coloring of quoted atom escape 
    sequences and of the built-in predicate at_end_of_stream/0 to the 
    Source-highlight package.

    Added missing support for the syntax coloring of the built-in predicate 
    at_end_of_stream/0 and of the scope operator ::/2 to the Kate text editor.
    Improved syntax coloring of parametric object opening directives.

    Added missing support for the syntax coloring of the built-in predicate 
    unify_with_occurs_check/2 to the Emacs text editor. Corrected a bug in 
    the syntax coloring of arithmetic comparison operators.

    Added missing support for the syntax coloring of quoted atom escape 
    sequences and of the built-in control construct call/1 to the 
    GtkSourceView 2.x text widget.

    Added missing support for the syntax coloring of variables, of quoted 
    atom escape sequences, of the built-in method clause/2, of the external 
    call Logtalk control construct {}/1, and of variables to the Nedit text 
    editor. Corrected a bug with 0'Char constants and corrected some typos 
    in the support for the current_event/2, implements_protocol/2-3, and 
    abolish_category/1 built-in predicates.


2.31.5 - April 29, 2008

    Added support for checking arithmetic expressions for calls to 
    non-portable functions when using the "portability" compiler flag.

    Updated the implementation of the threaded/1 built-in predicate to 
    ensure that thread creation errors (usually, virtual memory address 
    space exhaustion) result in the corresponding exception rather than 
    in a non-terminating call. Improved cancellation of all individual 
    threads when one of them terminates with an exception or a failure.

    Simplified the terms used to post individual results from threaded/1
    calls to the queue associated to the call.

    Corrected a bug in the built-in predicate threaded/1 when its argument 
    is a conjunction (disjunction) of conjunctions (disjunctions).

    Added a workaround for a mutex creation error when reloading a source 
    file with entities defining synchronized predicates.

    Updated the Logtalk runtime to unlock all mutexes hold by a thread when 
    upon thread cancellation.

    Corrected a Logtalk compiler bug that allowed a predicate to be declared 
    both dynamic and synchronized. Thanks to Paul Crocker for the bug report.

    Corrected a Logtalk compiler bug where local definition clauses for 
    dynamic predicates are being generated for categories. Thanks to Victor 
    Noel for the bug report.

    Updated the YAP and SWI-Prolog config files to set the default value of 
    the "tmpdir" flag depending on the host operating-system. Added missing
    declaration for the multi-threading predicate thread_initialization/1.

    Added missing declarations for some proprietary built-in meta-predicates 
    to the B-Prolog config file.

    Corrected a bug in the SWI-Prolog config file in the declaration of the 
    proprietary built-in meta-predicate "soft cut". Thanks to Victor Noel 
    for the bug report.

    Updated the XSB config file to use the new optimized call/N predicates 
    found on the current XSB CVS version.

    Added an integration script, "xsbmt64lgt", for using Logtalk with the 
    multi-threaded, 64 bits version of XSB.

    Simplified building of MacOS X Installer packages. Updated the Windows 
    installation script to use the "C:\lgtsvn" as base. Simplified manual 
    installation instructions.

    Updated the definitions of the predicate valid/1 for the library objects 
    "list", "list(Type)", "numberlist", "set", "set(Type)", "varlist" to fail 
    for lists with unbound tails after discussion with Jan Wielemaker and 
    Ulrich Neumerkel.

    Corrected a bug in the library object "lgtunit" when running "throws" 
    tests (make sure the generated exception is subsumed by the expected 
    exception). Added a "lgtunit_loader" loader utility file for loading 
    the Logtalk unit test library.

    Added a simple example, "debug_hooks", of using compilation hooks and 
    term expansion for conditional compilation of debug statements.

    Updated the "primes" multi-threading example to allow any number of 
    threads to be used in the computation of primes numbers.

    Added a new multi-threading example, "integration", implementing 
    Recursive Gaussian Quadrature Methods for Numerical Integration for 
    functions of a single variable, contributed by Paul Crocker.

    Added a new multi-threading example, "mtbatch", for benchmarking 
    multi-threading performance.

    Added a new example, "ack", implementing the Ackermann function (general 
    recursive function).

    Added support for using the Highlight package (version 2.6.9 or later) 
    by Andre Simon with Logtalk source files.

    Updated the TextMate Logtalk bundle and its configuration instructions 
    to make the "Compile" and "Generate ..." commands more general, making 
    it compatible with most Prolog compilers. Added syntax coloring for 
    standard arithmetic functions. Added a command for generating plain text 
    files from XML documenting files.

    Corrected a syntax coloring bug with character codes using the 0'Char 
    notation in the SubEthaEdit 2.x and Vim text editors and in the
    source-highlight package.

    Removed some redundant regular expressions from the jEdit text editor 
    syntax coloring support files.

    Corrected syntax coloring bugs with variables starting with underscores 
    (including anonymous variables) and with atoms containing an underscore 
    in the Emacs text editor. Thanks to Joerg Schuster for the bug report.

    Updated the Logtalk grammar documentation to reflect the changes to 
    category relations introduced in version 2.31.0.

    Added a "lgttxt.xsl" XSLT style-sheet and two shell scripts, "lgt2txt.sh" 
    and "lgt2txt.js", for converting XML documenting files into text files.
    Updated the "lgt2*.sh" shell scripts for POSIX compliance, removing 
    dependencies on bash shell features.

    Updated the "lgtxml.xsl" XSLT style-sheet to ensure that the generated 
    HTML files are fully compliant with the HTML 4.01 standard.

    Updated the Debian installer package shell scripts for POSIX compliance, 
    removing dependencies on bash shell features.


2.31.4 - February 20, 2008

    Optimized the performance of threaded/1 calls by using a per-call 
    message queue for collecting the individual call results and by 
    using the message queue identifier as a tag for the individual 
    calls. This solution avoids runtime synchronization of a large 
    number of threads on the same message queue, simplifies compilation 
    and runtime handling of threaded/1 calls, and simplifies thread 
    cancellation, eliminating any risk of dangling individual thread 
    results.

    Removed two redundant calls to the built-in predicate thread_exit/1 
    on the Logtalk compiler.

    Corrected a bug where a competitive or-parallelism call would 
    prematurely fail with one or more individual calls still pending.

    Corrected a bug where a competitive or-parallelism call would succeed 
    when all the individual calls had failed.

    Corrected a bug when compiling calls to the Logtalk multi-threading 
    built-in predicates made from the top-level interpreter, i.e. from 
    within the pseudo-object "user".

    Added foreach/3, forto/5, and fordownto/5 meta-predicates to the 
    library object "loop". Updated the definitions of the forto/3-4 
    and fordownto/3-4 meta-predicates to allow the use of arithmetic 
    expressions as arguments for convenience and clarity.

    Corrected a bug in the implementation of the predicate lookup/3 in 
    the library object "bintree".

    Added a multi-threading example of the Fast Fourier Transform, "fft", 
    contributed by Paul Crocker.

    Corrected a bug in the implementation of the bisection algorithm in 
    the multi-threading example "functions". Added an implementation of 
    the MATLAB humps function (contributed by Paul Crocker).

    Updated the multi-threading example "sorting" to workaround a mutex 
    performance issue with XSB when generating lists of random numbers.

    Updated support for the TextMate text editor. Added a command for 
    generating the PDF documentation of open source files. Added missing 
    tab triggers to the Logtalk snippets. Updated installation notes.

    Corrected a bug in the jEdit syntax coloring support for the is/2 
    operator.


2.31.3 - January 28, 2008

    Added a "VERSION.txt" file that is used to check compatibility between 
    an existing Logtalk user folder (whose path is stored in the LOGTALKUSER 
    environment variable) and a new Logtalk version.

    Updated the POSIX Prolog integration scripts to check for an outdated 
    Logtalk user folder, creating a new one if necessary by running the 
    "cplgtdirs" script (a backup is automatically made of the old directory).

    Updated the Windows installer to create a registry key with the Logtalk 
    version number and to check for an outdated Logtalk user folder.

    Changed the predicate used to load Prolog files, adding an additional 
    argument that represents a list of load/compile options (notably,
    encoding/1, which is necessary for supporting source files encodings 
    such as ISO-8859-X).

    Updated the SICStus Prolog 4 config file to also accept UCS-2 encodings 
    when using the encoding/1 directive (UCS-2 is subsumed by UTF-16).

    Added a workaround to the Quintus Prolog integration scripts for its 
    lack of support for expanding environment variables in file names.


2.31.2 - January 21, 2008

    Extended compatibility of the experimental Logtalk encoding/1 directive 
    to CxProlog 0.96.3 and SICStus Prolog 4.0.2 and improved support for YAP 
    and SWI-Prolog.

    Improved source file encoding handling by ensuring that a BOM present 
    in a source file being compiled is inherited by the generated Prolog 
    and XML files.

    Changed the atoms used to represent different encodings when using the 
    encoding/1 directive; Logtalk now uses the encoding names specified by 
    IANA (using the preferred MIME name whenever available).

    Updated the Logtalk compiler to throw an exception when the specified 
    encoding is not supported by the used back-end Prolog compiler.

    Updated the "encodings" example to use the new encoding names and added 
    new source files using UTF-16 and UTF-32 text encodings.

    Added POSIX and Windows integration scripts for Quintus Prolog.


2.31.1 - January 3, 2008

    Duplicated the range of threaded_call/2 tags for multi-threading Prolog 
    compilers with bounded integers.

    Updated the YAP config file to set the flag "language" to "iso". This 
    is not strictly necessary to run Logtalk with YAP but it helps prevent 
    nasty surprises when writing portable applications that rely on ISO 
    Prolog semantics.

    Updated the SWI-Prolog integration script to test for the availability of
    the XPCE library before trying to load the "xpcehook.pl" XPCE hook file.

    Updated the Linux (RMP and Debian) and MacOS X package build scripts to 
    include Prolog version compatibility information.

    Updated the "tak" multi-threading example to allow parameterization of 
    the number of threads to use.

    Updated the "sorting", "hanoi", and "fibonacci" multi-threading examples 
    to interpret the object parameter as the number of leaf threads (i.e. 
    working threads that will not recursively create additional threads).

    Updated the TextMate text editor support to include commands to compile 
    and to automatically generate the XHTML documentation of open source 
    files.


2.31.0 - December 21, 2007

    Added a new built-in protocol, "expanding", declaring goal_expansion/2
    and term_expansion/2 public predicates.

    Added compiler support for user-defined goal expansion hooks. Changed 
    the implementation of compiler term and goal expansion hooks to use 
    object-defined predicates term_expansion/2 and goal_expansion/2.
    Changed the compiler option "hook" to accept object identifiers.

    Allow a category to explicitly complement an existing object, thus 
    providing functionality similar to Objective-C categories. Added 
    complements_object/2 built-in predicate. Added a new example, 
    "complements", illustrating the new category functionality.

    When constructing a new category from other categories, the relation 
    "extends" is now used instead of the relation "imports". The relation 
    "imports" is now only used when an object imports a category. Added  
    extends_category/2-3 built-in predicates.

    Modified the built-in predicate define_events/5 to throw an existence 
    error instead of failing when the specified monitor object does not 
    exists. 

    Updated the Logtalk compiler to convert version numbers to atoms when 
    generating XML documenting files (thus avoiding problems with some 
    Prolog compilers that resulted in version numbers with a large number 
    of fractional digits).

    Improved updating of runtime bookkeeping tables when loading source 
    files.

    Renamed the predicate property "alias/1" to "alias_of/1" in order to 
    disambiguate its meaning.

    Added a new config file, "k6.config", for the K-Prolog 6.0 beta 
    version.

    Updated the B-Prolog config file to recognize mode/1 directives.
    Added some missing meta-predicate specifications to the config files 
    of XSB and YAP.

    Updated the Windows GUI installer to support running Logtalk with 
    CxProlog 0.96.1 and later versions.

    Added two new multi-threading examples, "fibonacci" and "hanoi", and 
    corrected a bug in the recursive creation of threads on the "sorting" 
    example. Updated the "primes" multi-threading example to also support 
    eight threads.

    Updated the "hooks" example for illustrating goal expansion hooks in 
    addition to term expansion hooks.

    Updated the "engines" example for compliance with the changes made 
    to category relations.

    Added syntax coloring support for the new goal_expansion/1, 
    complements_object/2, and extends_category/2-3 predicates to all 
    supported text editors.

    Updated the TextMate code snippets to use the TM_FULLNAME variable 
    instead of the deprecated "niutil" command to retrieve the user full 
    name. Thanks to Michael Sheets for the update. 


2.30.8 - November 9, 2007

    Fixed bug in the compilation of synchronized predicates that breaks 
    Logtalk on single-threaded Prolog compilers.


2.30.7 - November 5, 2007

    Updated the multi-threading built-in predicates threaded_notify/1 and 
    threaded_wait/1 to accept lists of notifications.

    Added a new read-only compiler flag, "context_switching_calls", allowing 
    context switching calls to be disabled (they are enabled by default).

    Updated the B-Prolog config file to recognize eager_consume/1 directives.
    Updated the XSB config file to recognize use_subsumptive_tabling/1,
    use_variant_tabling/1, index/1, thread_private/1, and thread_shared/1 
    directives.
    Updated the YAP config file to recognize thread_local/1 directives.
    Updated the SICStus Prolog config files to recognize volatile/1 directives.
    Updated the SWI-Prolog config file to recognize thread_local/1, index/1, 
    and hash/1 directives.

    Changed the backup directory names generated by the "cplgtdirs.*" shell 
    scripts to not include whitespace characters.

    Updated the "xsbmtlgt.sh" integration script to start XSB-MT using the 
    new command-line option "--shared_predicates" (requires current XSB CVS 
    version). Updated the Windows GUI installer to support running Logtalk 
    with XSB-MT.

    Added a multi-threading example, "barriers", of barrier synchronization.

    Updated the "functions" example sample queries for compatibility with the 
    ISO Prolog standard regarding representation of float numbers.

    Added a workaround for a parsing bug in XSB while compiling the "sicstus" 
    example.


2.30.6 - October 21, 2007

    Replaced calls to the proprietary current_thread/2 predicate in the 
    Logtalk runtime by calls to the thread_property/2 predicate as per 
    the ISO DTR on multi-threading predicates. Added a goal_expansion/2 
    clause to the SWI-Prolog config file to automatically switch between 
    the current_thread/2 and thread_property/2 predicates depending on 
    availability.

    Changed handling of the encoding/1 directive by the Logtalk compiler in 
    order to improve compatibility with YAP and SICStus Prolog. Removed from 
    the config files the now obsolete '$lgt_set_stream_encoding'/2 predicate 
    definition. Renamed the compiler option "supports_encoding_dir" to 
    "encoding_directive" and changed its possible values to "unsupported", 
    "full" (used in both Logtalk source files and compiler generated Prolog 
    files), and "source" (used only in Logtalk source files).

    Renamed compiler option "underscore_vars" to "underscore_variables".
    Renamed compiler option "supports_break_predicate" to "break_predicate".

    Improved the performance of recursive predicate definitions synchronized 
    by mutexes. Explicitly create all mutexes used by an entity at load time 
    for compatibility with XSB. Several changes to multi-threading support in 
    order to improve compatibility with current and forthcoming versions of 
    YAP, SWI-Prolog, and XSB.

    Updated the Logtalk compiler for compatibility with both logical and 
    immediate update semantics when compiling synchronized predicates.

    Updated the meta-predicate compilation sanity checks to verify the 
    existence of the minimum number of normal arguments in a clause head 
    required by the closure of maximum arity.

    Added a workaround for the lack of built-in support for character 
    unbuffered input when using the Logtalk built-in debugger to the config 
    files of ALS Prolog, B-Prolog, Ciao, CxProlog, IF/Prolog, JIProlog, 
    Prolog II+, SICStus Prolog, XSB, and YAP. Thanks to Parker Jones for the 
    bug report.

    Updated the YAP config file to auto-detect working Unicode support when 
    setting the "encoding_directive" compiler option.

    Updated the XSB config file to auto-detect multi-threading support
    when setting the "threads" compiler option. Added an integration script 
    (xsbmtlgt.sh) and supporting files for the multi-threaded version of XSB 
    (requires current development version, available from the XSB CVS server).

    Added a MacPorts portfile for building MacOS X installer packages.

    Added a BOM to the "babel.lgt" UTF-8 file in the "encodings" example in 
    order to improve compatibility with SICStus Prolog.

    Updated the library object "random" by replacing the synchronized/0 
    directive by a synchronized/1 directive listing only the predicates 
    that modify the random number seed.

    Added syntax coloring support for the GtkSourceView 2.x text widget 
    (used e.g. on the Gnome's Gedit text editor and on the MonoDevelop IDE).
    Removed syntax coloring for the obsolete atomic/1 predicate directive 
    from the support files of Source-highlight, Emacs, SubEthaEdit, jEdit, 
    and Kate. Optimized the regular expressions used in most syntax coloring 
    configuration files of supported text editors.


2.30.5 - September 19, 2007

    Added new multi-threading built-in predicates threaded_call/2, 
    threaded_once/2, threaded_exit/2, and threaded_peek/2. These new 
    predicates support the use of threaded call identifier tags in order to 
    link specific threaded_call/2 and threaded_once/2 calls to specific 
    threaded_exit/2 and threaded_peek/2 calls. Extended the "nondet" example 
    in order to illustrate the new functionality.

    Changed the implementation of the built-in predicate threaded_exit/1 in 
    order to avoid blocking when its argument is subsumed by the argument of 
    the corresponding threaded_call/1 call instead of being a variant.

    Updated the Logtalk compiler to encapsulate resource errors inside 
    error/2 exception terms (as specified in the ISO Prolog core standard).

    Corrected a bug in the library object "lgtunit" (wrong arity on two 
    failed_test/2 predicate calls).

    Corrected two problems with the "testing" example: a wrong call on the 
    object "dyn_tests" and a missing entry in the "libpaths.pl" file. Removed 
    two pointless dynamic predicate directives in the "buffer" example.

    Improved documentation of multi-threading programming and predicate 
    properties. Corrected the reference manual page describing the threaded/0 
    directive.

    Simplified installation scripts by moving shared distribution cleaning 
    code into the "cleandist.sh" script. Updated the "install.sh" script to 
    set the installation prefix to "/usr" on Debian systems. Updated the 
    Linux RPM spec file in order to clean the building directory after the 
    package creation.


2.30.4 - August 22, 2007

    Allow the argument of {}/1 calls to be a variable at compile time.

    Updated the Qu-Prolog config file to match and require version 8.1 and 
    added a "qplgt" integration script.

    Updated the XSB config file to match and require version 3.1 and to 
    take advantage of the compiler option optimize/1 when loading Logtalk 
    generated Prolog intermediate files.

    Added a new library object, "lgtunit", providing preliminary support for 
    writing and running unit tests. Added a new example, "testing", defining 
    sample unit tests.

    Added a new multi-threading example, "threads/tak", implementing the 
    Takeuchi function (recursive arithmetic).

    Updated the "threads/philosophers" example to use notifications instead 
    of a dynamic predicate for representing chopstick availability. Added an 
    alternative implementation using a parametric object. Improved example 
    documentation.

    Updated the "benchmarks" example to allow comparisons between calls to 
    imported category predicates and calls to local object predicates.

    Updated Emacs support in order to fix problems with the syntax-coloring 
    of some Logtalk built-in predicates and applied a patch contributed by 
    Nicolas Pelletier to workaround a compatibility problem with XEmacs.

    Updated jEdit support in order to fix a problem with the syntax-coloring 
    of the :/1 control construct.


2.30.3 - July 9, 2007

    Updated the multi-threading built-in predicate threaded/1 to support 
    both conjunctions of goals (akin to and-parallelism) and disjunctions 
    of goals (akin to or-parallelism) as an argument.

    Removed the experimental threaded_race/1 multi-threading built-in 
    predicate (its or-parallelism functionality is subsumed by the updated 
    threaded/1 predicate).

    Corrected a bug in the implementation of the multi-threading built-in 
    predicate threaded_exit/1 when there are more than one thread running 
    the same non-deterministic goal (the fix ensures that all alternative 
    solutions per threaded_exit/1 call come from the same computing thread). 
    Thanks to Paul Crocker for the suggested bug fix solution.

    Updated the sample queries in the "threads/buffer"/SCRIPT.txt" file to 
    match the updated entities in the example.

    Updated the "threads/functions" example to use the new version of the 
    threaded/1 multi-threading built-in predicate.


2.30.2 - June 24, 2007

    Updated the Logtalk compiler to throw a compilation error when duplicated 
    or conflicting predicate scope directives are found.

    Updated the Logtalk compiler to correct a cosmetic glitch when reporting 
    compilation errors.

    Updated the Logtalk compiler to check for mismatches between the argument 
    of this/1 calls and the parametric object identifier.

    Corrected a bug in the implementation of the multi-threading built-in 
    predicate threaded_ignore/1.

    Revamped the "threads/buffer" example to support setting the buffer 
    maximum number of items.

    Added a new DCG example, "dcgs/morse.lgt", for parsing messages in Morse 
    code.

    Extended the "parametric" example to illustrate a solution for dealing 
    with inheritance when defining "setter" predicates/methods that return 
    updated object identifiers.


2.30.1 - June 12, 2007

    Added a new, experimental control construct, :/1, for calling imported 
    category predicates without using message sending mechanisms.

    Added preliminary support for static binding when calling imported 
    category using the new :/1 control construct for categories compiled 
    and loaded using the compiler option "reload(skip)".

    Added a new control construct, <</2, which allows proving a goal within 
    the context of a specified object. Useful for debugging and for writing 
    object unit tests.

    Improved multi-threading support in order to make the built-in predicate 
    threaded_exit/1 generate an exception instead of blocking indefinitely 
    waiting for a reply from a non-existing thread.

    Updated the Logtalk compiler to generate an error when compiling from a 
    source file new definitions for built-in entities.

    Updated the Logtalk compiler to generate simpler clauses for the book-
    keeping table of local predicate definitions for parametric entities.

    Updated the config files for ECLiPSe, Ciao Prolog, SICStus Prolog, 
    SWI-Prolog, and YAP to use the renamed hook predicates introduced in 
    Logtalk 2.30.0 for parsing Prolog proprietary directives.

    Updated the "benchmarks" example to compare the performance of calls to 
    imported category predicates when using a message to "self" and a direct 
    call.


2.30.0 - May 28, 2007

    Added preliminary support for static binding when sending messages to 
    objects compiled and loaded using the compiler option "reload(skip)".

    Allow non-instantiated arguments at compile time for the multi-threading 
    built-in predicate threaded/1.

    Simplified and optimized the implementation of Logtalk multi-threading 
    support. Use a single dispatcher thread for all objects instead of each 
    object running its own dispatcher in order to minimize the number of 
    created threads (which can be problematic on 32 bits systems). Updated 
    the built-in predicate threaded/1 to make it deterministic and opaque to 
    cuts (similar to once/1).

    Updated the Logtalk built-in database methods to always interpret rules 
    whose body is the control construct true/0 as facts. Corrected a bug when 
    compiling dynamic predicates that would prevent using of the clause/2 
    built-in database method. Corrected a bug when using the Logtalk built-in 
    database method clause/2 with entities compiled in debug mode. Improved 
    predicate lookup caching when asserting and retracting dynamic facts.

    Improved detection and reporting of entity existence errors.

    Added a quit option, "q", to the Logtalk built-in debugger. Modified 
    the debugger behavior to automatically switch to trace mode when a spy 
    point is found.

    Added two new compiler options, "xmldir" and "tmpdir", allowing per 
    project definition of directories for storing XML documenting files 
    and for storing intermediate compilation files (e.g. Prolog files).
    Removed the config file predicate '$lgt_alt_directory'/2.
    Older config files are incompatible with this new Logtalk version.

    Added a shortcut to the Logtalk built-in predicate logtalk_load/1, {}/1,
    to all config files (defined there in order to be easy to comment it out 
    in case of conflict with some Prolog native feature or lack of compliance
    with the ISO Prolog standard regarding the definition of the {}/1 syntax.

    Allow the compiler flag "misspelt" to be set to "error".

    Updated the Logtalk compiler to not try to clean-up the dynamic predicates
    of redefined entities when reloading source files. Most Prolog compilers 
    already behave as expected when reloading the intermediate Prolog files 
    generated by the Logtalk compiler. For those Prolog compilers that do not 
    replace old definitions for dynamic predicates with the new ones, it is 
    not possible for Logtalk to implement a workaround that would work 
    correctly in all cases. Consult the "configs/NOTES.txt" file for more 
    information.

    Corrected a bug that prevents abolishing a dynamic entity loaded from a 
    source file. Thanks to Victor Noel for the bug report.

    Renamed the '$lgt_copy_pl_directive'/1 and '$lgt_rewrite_pl_directive'/2 
    config files predicates to '$lgt_rewrite_and_copy_pl_directive'/2 and 
    '$lgt_rewrite_and_recompile_pl_directive'/2. 

    Updated the config file for B-Prolog to match (and require) the new 7.0 
    version; updated and simplified the corresponding integration scripts.

    Updated the XSB POSIX integration script to automatically detect if we 
    are running the XSB stable version of the XSB CVS version.

    Added basic support for tabling to the config files of B-Prolog, XSB, 
    and YAP. Added a simple example of using tabling directives within 
    objects.

    Updated the SWI-Prolog and YAP config files to automatically detect if 
    the Prolog systems have been compiled with multi-threading support and 
    to set the Logtalk compiler flag "threads" accordingly.

    Corrected a bug when running Logtalk with SWI-Prolog that prevented the 
    use of alternative compilation directories (i.e. turning on the "altdirs" 
    compiler flag). Corrected a bug when running Logtalk with SWI-Prolog that 
    can prevent make/0 from recompiling and reloading modified Logtalk source 
    files. Updated the SWI-Prolog integration script, "swilgt.sh", to more 
    reliably detect the compiler executable name.

    Added a "configs/swi_set_logtalk_context.pl" file defining a useful but 
    fragile hack implementing a set_logtalk_context/1 built-in predicate for 
    switching the Logtalk top-level execution context to objects other than 
    the default pseudo-object "user" (you may use it as a debugging tool).

    Updated the CxProlog config file to use the new built-in predicates in 
    version 0.95. Added a shell script, "cxlgt.sh", for easy integration of 
    Logtalk with CxProlog on POSIX systems (with the help of Artur Miguel 
    Dias, CxProlog author).

    Updated the Ciao, K-Prolog, and ECLiPSe config files to set the default 
    value for the compiler flag "underscore_vars" to "dont_care" in order to 
    avoid spurious warnings with some of the provided examples.

    Added a config file and integration scripts for the current XSB CVS 
    version (3.0.1+), which supports some features needed by Logtalk not 
    present in the current stable version (namely, expansion of environment 
    variables).

    Added predicates depth/2 and variant/2 to the library object "term".

    Much improved "benchmarks" example, updated to allow running tests in 
    three different scenarios: event support on, event support off, and 
    using static binding. Moreover, metacalls are no longer used to run 
    the benchmark goals, resulting in more meaningful and accurate results.

    Removed all the "make_*lgt.*" and "makeall_lgt.*" shell scripts, replaced 
    by pre-made integration scripts that can be found on the new "integration"
    directory. Removed the "lgt_install.js" script. Renamed the POSIX install 
    and uninstall scripts to, respectively, "install.sh" and "uninstall.sh".
    Updated the integration, uninstall, and user-setup POSIX shell scripts 
    to use "$prefix/share/logtalk" as the default installation directory to 
    better comply with the Filesystem Hierarchy Standard 2.3 for UNIX-like 
    operating systems.

    Updated the integration scripts to automatically call the "cplgtdirs" 
    script when the Logtalk user directory cannot be located.

    Updated the integration, documentation, uninstall, and user-setup POSIX 
    shell scripts to try to locate the Logtalk installation directory and the 
    Logtalk user directory when the environment variables LOGTALKHOME and 
    LOGTALKUSER are not set.

    Updated the "install.sh" POSIX shell script to better clean and sanitize 
    the file permissions on the installation directory.

    Updated the "build_release.sh" POSIX shell script to also build a Debian 
    binary installer package (experimental).

    The Windows GUI installer no longer spans command-line shells running 
    JScript scripts to build the Prolog integration shortcuts. This hopefully 
    solves issues with security software silently blocking and breaking the 
    Logtalk installation.

    Added basic syntax coloring support for the GNU Nano 2.x text editor.


2.29.5 - March 28, 2007

    Added a new built-in predicate, threaded/1, for proving each goal in 
    a conjunction in its own thread, simplifying common multi-threading 
    tasks that previously required sequences of calls to the built-in 
    predicates threaded_call/1 and threaded_exit/1.

    Simplified and optimized the implementation of Logtalk multi-threading 
    support.

    Simplified implementation of the database built-in methods. Simplified 
    caching of dynamic predicate lookups. Improved performance of the 
    built-in methods retract/1 and retractall/1.

    Simplified the code generated when compiling entities in debugging mode.

    Corrected a bug in the built-in debugger when processing actions at a 
    port that implies reading a port action again (e.g. print exception term,
    print debugging status, and help options). Allow the debugger command 
    "skip" to work as the command "creep" in ports other than "call" and 
    "redo". Added a new debugger command, "ignore". Suspend debugging when 
    using the "break" debugger command.

    Generate a compilation error instead of just printing a warning when 
    compiling calls to the multi-threading built-in predicates within an 
    object with no threaded/0 directive present.

    Corrected a bug when compiling entities containing synchronization 
    directives on single-threaded Prolog configurations.

    Improving reporting of working directory when loading or compiling source 
    files by expanding any environment variables occurring in the path.

    Added a new compiler option, "reload", for defining the Logtalk behavior 
    when reloading source files. Valid values are "always" (default value; 
    defined in the config files) and "skip".

    Updated the programming examples to use the new "reload" compiler option 
    when loading library entities. Simplified loading of example source files 
    (by updating the utility loader files to automatically load all required 
    library files).

    Updated GNU Prolog config file to take advantage of some built-in list 
    predicates (requires version 1.2.14 or later); changed the compiler flag 
    "underscore_vars" value to "dont_care" to avoid spurious warnings with 
    some examples.

    Added a config file for B-Prolog 7.0b1.

    Updated the POSIX integration shell scripts to pass along any command 
    line options to the corresponding Prolog compiler and to prevent some 
    problems with paths containing spaces.

    Much improved syntax coloring and code completion support for the jEdit 
    text editor.

    Updated the "threads/primes" example to use the new "threaded/1" built-in 
    predicate. Updated the "threads/birthdays" example to better illustrate 
    the use of the built-in multi-threading predicates. Added a new 
    multi-threading example, "msort", implementing single-threaded and 
    multi-threaded versions of the merge sort algorithm.

    Expanded the "operators" example to illustrate a simple solution for 
    making operators local to source files (but global to all entities 
    defined within the source files).


2.29.4 - February 19, 2007

    Added a new library category, "listing", defining listing/0 and 
    listing/1 methods for helping in debugging tasks.

    Added two new experimental multi-threading predicates, threaded_wait/1 
    and threaded_notify/1, which allows suspension of a thread's goal until  
    a notification is received. Added two new examples, "threads/buffer" and 
    "threads/blackboard", illustrating the use of these predicates.

    Simplified and changed implementation of the threaded built-in 
    predicates in order to ensure that the threaded/0 directive is only 
    required on objects calling these predicates.

    Only print a warning for a missing threaded/0 directive for objects.

    Corrected a ordering bug on the entity initialization goal that 
    prevented using an object initialization goal that make use of 
    the object thread. 

    Corrected a bug when asserting rules into an object's database that    
    resulted in only the first asserted rule being visible when calling 
    the predicate through message sending. Thanks to Parker Jones for 
    the bug report.

    Corrected a bug when compiling dynamic entities (defined in source 
    files using the dynamic/0 directive) where declared predicates would 
    be wrongly compiled as static instead of dynamic.

    Updated the "make_xsblgt.sh" integration script again to fix an 
    additional problem resulting from the lack of support in XSB for 
    using environment variables in file paths.

    Added minimal support for using Exuberant Ctags with Logtalk.

    Added auto indent support to the jEdit text editor.

    Added support for listing public predicates in the "Functions" window 
    of the SuperEdi text editor.

    Converted TextMate code snippets from the old Property List format 
    to XML in order to provide compatibility with the "e" Windows text
    editor.

    New example: 99 bottles of beer on the wall! Sing along!


2.29.3 - January 15, 2007

    Corrected a bug in the Logtalk compiler optimizer code which was 
    discarding some declaration and definition catchall clauses needed 
    by the Logtalk built-in database methods when there is no initial 
    declaration and definition for the referenced dynamic predicates.
    Thanks to Parker Jones for the bug report.

    Corrected a bug in the compilation of empty, standalone protocols 
    and categories.

    Updated the "make_xsblgt.sh" integration script to workaround 
    the lack of support in XSB for using environment variables in 
    the argument of the reconsult/1 predicate.

    Corrected a bug in the "potions.lgt" example puzzle that prevented 
    its solution of being found.


2.29.2 - January 10, 2007

    Silently compile synchronized predicates as normal predicates on 
    single-threaded Prolog compilers.

    When using the threaded_race/1 predicate, competing threads are 
    now created detached.

    Corrected a bug that resulted in a loading error when reloading 
    source files defining threaded objects.

    Corrected a bug in the implementation of the built-in predicate 
    threaded_peek/1 that prevented alternative solutions from being 
    retrieved using the built-in predicate threaded_exit/1. Removed 
    the built-in predicate threaded_discard/1.

    The library object "random" is now a synchronized object. Updated 
    the "philosophers" multi-threading example accordingly.

    Dropped loading of broken "cleanup" library from the YAP config file 
    (the call_cleanup/2 predicate, required for Logtalk multi-threading, 
    is now available as a built-in predicate in the YAP CVS version).


2.29.1 - December 28, 2006

    Added a Logtalk version of John Fletcher's Prolog XML parser (see the 
    folder "contributions/xml_parser").

    Added shell scripts for helping building the distribution files of a 
    new Logtalk release. Updated the MacOS X installer package to set 
    default values for the Logtalk environment variables. Corrected a bug 
    in the "logtalk.spec" file where the default value for the LOGTALKUSER 
    environment variable only worked for the user doing the RPM installation.

    Corrected a bug in the reporting of the line number where a compilation 
    error (or warning) occurred. Extended support for reporting warning and 
    error line numbers to Quintus Prolog, Ciao Prolog, Qu-Prolog, and 
    ECLiPSe.

    Corrected a bug when using partial lists with the predicates nth0/3-4 
    and nth1/3-4 provided by the "list" library object.

    Improved "philosophers" multi-threading programming example.


2.29.0 - December 18, 2006

    Added a new built-in, empty object named "logtalk", which can play the 
    role of both a class and a prototype. It may be used to define class 
    hierarchies without forcing the use of metaclasses or reflective 
    designs.

    Added a built-in protocol named "monitoring" with declarations for 
    the before/3 and after/3 public event handler predicates. Updated 
    the Logtalk compiler to print a warning when defining an event handler 
    with no reference to the "monitoring" protocol.

    The default value of the compiler flag events/1 is now off. As most 
    applications do not use events, this setting ensures the best possible 
    message processing performance for those applications.

    Removed the experimental threaded_call/2 and threaded_exit/2 thread 
    predicates, replaced by new threaded_once/1, threaded_ignore/1, 
    threaded_race/1, threaded_peek/1, and threaded_discard/1 predicates.
    Renamed predicate directive atomic/1 to synchronized/1. Added new 
    entity directive synchronized/0. Added support for new "synchronized" 
    and "threaded" entity properties.

    Corrected a bug when using threaded calls as initialization goals 
    within threaded objects.

    Corrected an elusive bug in the Logtalk compiler where a source file 
    may not be properly closed when it contains a syntax error (thanks 
    to Robert Shiplett for the bug report).

    Corrected a bug in the implementation of the built-in methods retract/1 
    and retractall/1 that could result in unexpected exceptions. Updated 
    the built-in method assertz/1 to always use the lookup cache.

    Corrected a bug in the compilation of empty classes that are not 
    instances of a metaclass.

    Corrected a bug in the built-in method predicate_property/2 where some 
    predicate properties may not be returned when enumerating properties 
    using backtracking.

    Modified the SWI-Prolog config file and integration scripts to set 
    the flag "iso" to "true". Corrected an elusive bug in the definition 
    of predicate '$lgt_directory_exists'/1 that resulted in "library not 
    found" errors when loading Logtalk source files from within the 
    SWI-Prolog initialization file (thanks to Robert Shiplett for the bug 
    report).

    Updated the K-Prolog config file to workaround a problem when using 
    library notation due to failure to check directory existence with the 
    provided "libpaths.pl" file.

    Added a RELAX NG file describing the structure of the XML documenting 
    files generated by Logtalk.

    Corrected a bug in the Logtalk DTD file (missing "copyright" tag 
    declaration).

    Corrected a bug in the lgt2*.js scripts where the "custom.ent" file 
    was not being copied when generating (X)HTML and PDF files.

    Added a new multi-threading example, "philosophers", illustrating a 
    possible implementation of the "dining philosophers" problem.

    Improved the "metapredicates" example in order to illustrate the use 
    of closures instead of goals as meta-arguments.

    Added a reference to the "e" Windows text editor, which supports 
    the MacOS X TextMate 1.x text editor syntax configuration files.
    
    Updated the manuals index pages in order to workaround browsers bugs 
    with parsing of empty "span" tags (e.g. Internet Explorer and Opera).


2.28.2 - November 6, 2006

    Corrected a compiler bug where unknown entities will not be report when 
    compiling a source file whenever an entity with the same name but of a
    different type is already known.

    Added a XPCE hook file ("configs/xpcehook.pl") supporting Logtalk message 
    sending goals as XPCE call-back goals. The XPCE library is now loaded by 
    default by the SWI-Prolog integration scripts.

    Added support for generating single PDF files of the User and Reference 
    Manuals. Removed the PDF versions of the individual manual XHTML pages.

    The ECLiPSe config files now require release 5.10#26 or a later version.

    Added support for listing Logtalk entity names (objects, categories, and 
    protocols) in the SubEthaEdit symbols menu.

    Added a Vim dictionary file for Logtalk keyword completion and support 
    for automatic indentation.

    Added basic support for the MacOS X Smultron text editor. Added basic 
    support for the Notepad++, SuperEdi, and ConTEXT Windows text editors.


2.28.1 - October 10, 2006

    Added support for using XML entities using the notation "{entity name}" 
    in info/1 documenting directives for the "author", "copyright", and 
    "license" keywords. The XML entities are defined on a "custom.ent" file.

    Updated Logtalk bibliographic references (in file "BIBLIOGRAPHY.bib").

    Added a "lgt_uninstall.sh" shell script for uninstalling Logtalk on POSIX 
    operating systems.

    Improved RPM install-time messages on the defined Logtalk environment 
    variables.

    Updated the ECLiPSe integration scripts and config files to work with 
    and require version 5.10 (the first open source version of ECLiPSe).

    Corrected a typo on the "logtalk.dtd" file that prevents validation of 
    XML documenting files that use a local reference to the DTD.


2.28.0 - September 28, 2006

    Updated the Logtalk license to the final version of the "The Artistic 
    License 2.0" (see http://www.perlfoundation.org/legal/ for details).

    Added experimental support for multi-threading programming on selected 
    Prolog compilers. Added a new object directive, threaded/0, a new 
    predicate directive, atomic/1, and four new built-in predicates, 
    threaded_call/1-2 and threaded_exit/1-2. Added a new set of examples, 
    "threads". Thanks to Paulo Nunes for helping developing and testing 
    these new features.

    Expanded support for meta-predicates by allowing the declaration of meta-
    arguments as closures instead of goals.

    Added the generalized call/N predicate as a built-in method. This built-in 
    method must be used in the implementation of meta-predicates which work 
    with closures instead of goals.

    The metapredicate/1 directive should be considered deprecated. Use the 
    meta_predicate/1 directive instead.

    Updated the Logtalk compiler to generate an error whenever a non-variable 
    meta-argument is found in a clause head of a user-defined meta-predicate.

    Improved compilation of meta-predicate meta-arguments. Corrected a bug 
    in the compilation of user meta-predicates that allowed illegal calls 
    to non-public predicates on the caller object to be made from the object 
    defining the meta-predicates. Thanks to Rémy Haemmerlé and François 
    Fages for reporting the problem.

    Improved performance for non-cached messages, notably when running with 
    YAP, GNU Prolog, and SWI-Prolog on all operating systems and with SICStus 
    Prolog 4.0 on POSIX operating systems.

    Updated the Logtalk compiler to generate an error whenever a predicate 
    directive appears in a source file after predicate clauses that call the 
    predicate specified in the directive.

    Added support for "copyright" and "license" keys to the info/1 entity 
    documenting directive.

    Improved compiler error messages to also report source file line number 
    for selected Prolog compilers.

    Added PDF versions of all the manual XHTML pages. Added links to all the 
    manual XHTML pages to the corresponding PDF versions.

    Corrected a bug (introduced in version 2.27.0) in the built-in predicates 
    abolish_object/1, abolish_protocol/1, and abolish_category/1 that resulted
    in some clauses not being retracted when an object is abolished (thanks to 
    Neng-Fa Zhou for the bug report).

    Corrected a bug (introduced in version 2.27.1) in the processing of the 
    term_expansion/2 predicate.

    Corrected a bug in the compilation of redefined built-in predicates with 
    no clauses.

    Added an experimental config file for CxProlog 0.93.1.

    Updated the SWI-Prolog config and hook files in order to support the 
    edit/1 and make/0 development predicates.

    Changed the Logtalk - SWI-Prolog integration scripts to load the hook 
    file "swihook.pl" after the other files in order to avoid some possible 
    errors at startup.

    Updated the config file for the forthcoming SICStus Prolog 4.0 version 
    to work in the current beta version. Modified the "make_sicstuslgt.*" 
    shell scripts to work with both SICStus Prolog 3.12 and 4.0 versions.

    Updated the config file for YAP to workaround a problem on the Windows 
    version where testing for directory existence fails if the path ends with 
    a slash (or a double backslash); this problem prevents the use of library 
    notation to load source files (problem already fixed in the current YAP 
    CVS version).

    Updated the config file for B-Prolog to match (and require) the new 6.9 
    version; added integration shell scripts (for both Windows and POSIX 
    systems).

    Updated the config files and the integration scripts for ECLiPSe in order 
    to workaround bugs on the predicates abolish/1 and canonical_path_name/2.
    Modified the "make_eclipselgt.js" script to work with both ECLiPSe 5.8 
    and 5.9 versions.

    Dropped support for versions of XSB older than 3.0. Added support for 
    smart compilation of source files to the XSB config file.

    Updated the config file for IF/Prolog 5.1 by adding a missing definition 
    for predicate retractall/1 and avoiding some harmless singleton warnings.

    Add a ".txt" extension to all "NOTES" and "SCRIPT" files.

    Extended "dcgs", "parametric", and "metainterpreters" examples.

    Added Inno Setup GUI Windows installer script.

    Update all the JScript scripts to check if a compatible version of WSH 
    is installed and to workaround some problems with spaces in file paths.

    Updated the "lgt_install.js" JScript script to copy the scripts/*.bat and 
    the xml/*.bat batch scripts to the system's Windows directory instead of 
    modifying the PATH environment variable.

    Updated the "cplgtdirs.*" shell scripts to make a backup copy of any 
    previous LOGTALKUSER directory.

    Added post-install scripts to the LINUX RPM "logtalk.spec" file for 
    setting the environment variable LOGTALKHOME for all users, defining 
    a default value for the environment variable LOGTALKUSER, and running 
    the Prolog integration scripts.

    Split the installation and customization instructions in two files, 
    "INSTALL.txt" and "CUSTOMIZE.txt".

    Added shell scripts for converting the manual XHTML pages into PDF files 
    using CSSToXSLFO.


2.27.1 - March 27, 2006

    Allow calls to the built-in method parameter/2 with the first argument 
    not instantiated at compile time. Detect and report as a compilation 
    error parameter/2 indexes that are out of range.

    Optimized generation of predicate definition and declaration linking 
    clauses, resulting in small lookup performance improvements and in space 
    savings for the Prolog code generated when compiling Logtalk entities.

    Many minor code and documentation improvements to the Logtalk compiler.

    Added an object version of the tokenizer described in the Michael 
    Covington's paper "Tokenization using DCG Rules" to the "dcgs" example.

    Improved integration code for Qu-Prolog and Logtalk ("configs/qphook.ql").

    Improved library hierarchy methods that return lists of objects in order 
    to avoid duplicated elements (library objects "proto_hierarchy.lgt" and 
    "class_hierarchy.lgt"). Added new methods extension/1 and extensions/1 to 
    the library object "proto_hierarchy.lgt".

    Documented the concept of "parametric object proxy". Added a new example, 
    "proxies", illustrating the use of parametric object proxies.

    Added support for code completion and for listing entity names on the 
    symbol pop-up menu to the MacOS X TextMate text editor.

    Updated the "cplgtdirs.*" scripts to also create an alias/shortcut to the 
    "wenv" directory.

    Renamed the alternative compilation and documentation directory names on 
    all config files to be compatible across operating-systems. Removed unused
    predicate '$lgt_reverse'/2 from all config files.

    Updated HTML manuals "print.css" CSS file for compatibility with the 
    latest version of CSSToXSLFO.


2.27.0 - February 9, 2006

    Improved performance for local calls to the built-in methods phrase/2-3.
    Allow the built-in methods phrase/2-3 to accept both partial and proper 
    lists of terminals.

    Improved grammar rule translator. Report calls to undefined non-terminals 
    when translating grammar rules.

    Added support for declaring grammar rule non-terminal aliases using the 
    alias/3 directive.

    Added a new predicate property, non_terminal/1, for predicates resulting 
    from the compilation of grammar rule non-terminals.

    Improved support for the built-in method expand_term/2 in order to allow 
    bypassing of the default Logtalk grammar rule translator by defining 
    clauses for the term_expansion/2 predicate. Added a "term_expansionp" 
    protocol to the Logtalk library. Added a new example, "expansion", 
    illustrating the use of the term_expansion/2 predicate.

    Added a new compiler flag, hook/1, allowing the specification of a 
    compiler hook that is called for which term read from a source file.
    Added a simple example, "hooks", of using the Logtalk compiler hook 
    to expand author abbreviations in info/1 directives into full names 
    and email addresses.

    Added support for XSB 3.x to the runtime error handler. Updated the XSB 
    3.x config file with declarations for multi-threading meta-predicates.
    
    Removed a few choice-points when checking validity of entity directives.

    Added two new objects, list(Type) and set(Type), to the standard library 
    supporting the validation of lists and ordered sets whose elements are 
    restricted to a single type.

    Added a new DCG example for solving enigmas encoded using a cellphone 
    keypad.

    Added a missing library dependency to the "puzzles" example SCRIPT file.

    Removed the experimental "systemp.lgt" protocol from the list of files 
    loaded by the "library/all_loader.lgt" loader utility files to avoid 
    compilation errors on some Prolog systems.

    Corrected a bug that prevented dynamic creation of categories using the 
    built-in predicate create_category/4.

    Corrected a bug in the reporting of singleton variables, which failed to 
    write an accurate message for facts and grammar rules.

    Corrected a bug in passing the correct calling context ("this") when 
    processing meta-calls in objects.

    Corrected a bug in scope checking with local calls to reflection and 
    database methods.

    Corrected a bug in checking the validity of the arguments of the op/3 
    directive appearing inside entities.

    Added predicates for testing if a term is a partial list or a proper list 
    to all config files.

    Added a definition for missing open/4 ISO Prolog predicate to the config 
    file of Bin Prolog.

    Added a workaround for a B-Prolog bug to this compiler config file.


2.26.2 - December 20, 2005

    Improved error-checking for the Logtalk compiler and for the grammar rule 
    translator.

    Small performance improvements for message sending and for the built-in 
    database methods.

    Corrected a bug on the implementation of the built-in methods phrase/2-3 
    for negated grammar rule bodies (thanks to Mats Carlsson for pointing the 
    error).

    Removed the read-only compiler flag "iso_initialization_dir".

    Corrected a compilation bug on the "metapredicates" example source file.
    Corrected several bugs on the performance monitor of the "searching" 
    example.

    Switched off default generation of XML documenting files for the "symdiff" 
    example in order to avoid file names compatibility problems on Windows.

    Updated compatibility notes on B-Prolog 6.8 and Qu-Prolog 7.0. Added a 
    config file for the forthcoming SICStus Prolog 4.0 version (based only 
    on publicly available information). Updated the config file for Amzi! 
    Prolog to solve issues with predicate properties and to ensure that file 
    system utility predicates are loaded.

    Added a config file for the current XSB CVS version and the corresponding 
    integration shell scripts (for both Windows and POSIX systems). Modified 
    the "cplgtdirs.*" shell scripts in order to make either links or copies of
    the config files and the "libpaths.pl" file with the required ".P" file 
    name extension.

    Improved integration scripts documentation and help screens.

    Added a predicate for checking directory existence to the config files.


2.26.1 - November 28, 2005

    Added a CSS style-sheet to the Logtalk XHTML documentation that can be 
    used with CSSToXSLFO to generate nicely formatted PDF files suitable for 
    printing with running headers and page numbers.

    Updated the Logtalk XHTML documentation for compliance with the XHTML 1.1 
    standard.

    Updated the "lgtxhtml.xsl" XSLT file in order to generate XHTML 1.1 files.

    Added a new, generic "lgtpdf.xsl" XSLT file. Redefined the "lgtpdfa4.xsl" 
    and "lgtpdfus.xsl" files to import the "lgtpdf.xsl" file.

    Added support for the Lunasil XSL-FO processor to the "lgt2pdf.*" shell 
    scripts.

    Updated the "lgt2pdf.sh", "lgt2xml.sh", and "lgt2html.sh" shell scripts 
    in order to write a warning message when the current directory does not 
    contain any XML documenting file.

    Added a definition for missing open/4 ISO Prolog predicate to the config 
    files of Open Prolog, LPA Prolog compilers, and MasterProlog.


2.26.0 - November 7, 2005

    Added support for defining predicate aliases when using uses/2 directives
    (using the format Predicate::Alias).

    Added Prolog modules migration code allowing modules to be compiled as 
    objects and allowing messages to be sent to modules. Added a new "modules"
    example.

    Added a "Prolog Integration and Migration Guide" to the Logtalk 
    documentation.

    Added support for syntax coloring of common Prolog module directives to 
    the configuration files of the supported text editors.

    Added support for using library aliases on the second argument of the 
    logtalk_library_path/2 predicate (using the format alias(path)).

    Added support for ignoring, copying as-is, or rewriting proprietary Prolog
    directives. The action to be taken is defined on a per-directive basis on 
    the config files.

    Updated the config files of CIAO, ECLiPSe, SWI-Prolog, and YAP to define 
    actions for some proprietary directives in order to allow some or most of 
    the module libraries distributed with these compilers to be compiled as 
    objects.

    Renamed some XML documentation-related compiler flags to more meaningful 
    names: "xml" -> "xmldocs", "xsl" -> "xslfile", and "doctype" -> "xmlsref".
    No changes to the other flags or flag valid values.

    Updated documenting scripts to use system-wide resources from LOGTALKHOME
    and user-modifiable resources from LOGTALKUSER.

    Updated "cplgtdirs.*" shell scripts to create links to the documenting 
    scripts and to the DTD and XML Schema specifications instead of making 
    local copies. Updated the "cplgtdirs.js" Windows JScript script to create
    a link to the Logtalk manuals.

    Changed generation of predicate compiled functors to add an underscore 
    between the original predicate functor and arity (further minimizing the 
    chance of name conflicts).

    Improved compilation warning messages (separately handling plural and 
    singular forms).

    Improved documentation of Windows JScript installation and integration 
    scripts.

    Corrected a bug on the Logtalk built-in debugger on the processing of the
    abort option at a leashed port (option was ignored instead of aborting the
    debugging session).

    Added an option to choose between a "verbose" or "compact" listing of the 
    default compilation flags at Logtalk startup (defined on the config files).

    Improved CIAO integration scripts in order to suppress some (harmless) 
    warnings which are generated at first run.

    Updated SWI-Prolog hook file ("swihook.pl") in order to support Logtalk 
    library notation when loading Logtalk files using the SWI-Prolog consult/1 
    predicate.

    Corrected a bug on the implementation of the built-in method abolish/1 
    that prevented abolishing of dynamic predicates with arity zero.

    Corrected a bug on the "gplgt" shell script generated by the make_gplgt.sh
    shell script where the value of the LOGTALKHOME environment variable would
    not be retrieved at runtime.

    Removed config file for older versions of XSB (up to 2.6). Renamed the 
    config file for XSB 2.7.1 to simply "xsb.config".

    Consolidated the source files of the "birds", "errors", "lpa", "lo", 
    "metainterpreters", "poem", "relations", "roots", and "symdiff" examples 
    into single source files. Updated the "searching" example to take advantage
    of the uses/2 directive.

    Removed outdated documenting shell scripts from the "xml" directory.

    Corrected a bug when compiling a source file where the generated Prolog 
    file might not be properly closed when a compilation error occurs.


2.25.3 - September 12, 2005

    Consolidated the source files of the examples "bricks", "dynpred", "mi", 
    "parametric", "points", "polygons", "reflection", "shapes", "sicstus", 
    and "viewpoints" into single source files.

    Improved documentation on most example source files. Improved "parametric"
    example by adding a new parametric objects and by illustrating alternative
    ways of accessing object parameters.

    Updated several config files with declarations for some more non-standard 
    Prolog meta-predicates.

    Corrected some omissions and typos on the B-Prolog - Logtalk integration 
    instructions.

    Small performance optimization for messages and super-calls with not yet
    cached method lookups.


2.25.2 - August 11, 2005

    Updated Logtalk installation and Prolog integration scripts in order to 
    detect a wrongly defined LOGTALKHOME environment variable.

    Corrected a bug on the lgt_install.sh and make*lgt.sh shell scripts where 
    the wrong variable was being referenced when testing the existence of the 
    installation directory prefix.

    Corrected a bug on the makeall_lgt.sh shell script that failed to properly
    detect unsuccessful completion of individual Prolog integration scripts. 


2.25.1 - August 8, 2005

    Added support for using the "source-highlight" package (version 2.0 or 
    later) by Lorenzo Bettini with Logtalk source files.

    Several optimizations to the syntax coloring configuration files of most 
    of the supported text editors. Added support for code folding to the Vim, 
    Kate, and TextMate text editors.

    Updated the SWI-Prolog shell integration script (make_swilgt.sh) to use 
    either "swipl" or "pl" as the name of the Prolog executable, depending 
    on the host operating system.

    Modified the way entity prefixes are generated for compiled code in order 
    to further minimize possible conflicts resulting from the same prefix being
    used for different entities (bug report and fix by Brian Hulley). Changes 
    to the prefix format are also reflected on the names of the automatically 
    generated XML documenting files.

    Updated the lgt2html.* and lgt2xml.* documenting scripts in order to index 
    parametric objects using the notation <entity>/<number of parameters>.

    Corrected a bug on the lgtxml.xsl XSLT file where links to related files 
    pointed to .html files instead of .xml files.

    Updated the lgt_install.sh and the make_*lgt.sh shell scripts to check and
    report invalid installation directory prefixes.

    Added a new state-space search problem, "salt3.lgt", contributed by Paula 
    Marisa Sampaio, to the "searching" example.


2.25.0 - May 23, 2005

    Logtalk compiler is now source file-based instead of entity-based. Thus, 
    a source file may now contain any number of entities, without the need of 
    using source metafiles. Therefore, this version drops support for source 
    metafiles and the .mlgt file name extension.

    The experimental encoding/1 directive, when used, must be the first term 
    on a source file.  Added an entry to the reference manual describing the 
    directive. Improved "encodings" example.

    Added a new method, debugging/1, to the "debugger" pseudo-object for 
    querying the system about entities compiled in debug mode.

    Improved source file and entity compilation and loading reporting. In 
    particular, when using library notation for source files, the Logtalk 
    compiler now prints the library path containing the source files being 
    compiled or loaded.

    Added new shell scripts, makeall_lgt.*, which run all the make_*lgt.* 
    shell scripts in sequence.

    Simplified compiler reporting of singleton variables in directives and 
    clauses.

    Added an adaption of the "timetables" LPA Prolog++ example.

    Updated B-Prolog config file for the new 6.7 #2 version. Dropped support 
    for older versions of B-Prolog.


2.24.0 - April 22, 2005

    Added experimental support for a encoding/1 directive for declaring the 
    text character encoding of a source file. This directive is fully based 
    on a directive with the same name and with similar semantics found on 
    recent development versions of SWI-Prolog. For now, this directive only 
    works with SWI-Prolog as most Prolog compilers lack support for dealing 
    with different text encodings. Added new flag "supports_encoding_dir". 
    Added a new example, "encodings", of using the new encoding/1 directive.

    When a source file contains an encoding/1 directive, the XML documenting 
    files will use the same encoding. When no encoding/1 directive is present,
    the XML documenting files will assume UTF-8 encoding.

    Added new info/1 documenting directive key, "parameters", allowing the 
    declaration of both parameter names and parameter descriptions. Added new 
    info/1 documenting directive key, "remarks", allowing general remarks 
    about an entity to be stated. Added new info/2 documenting directive key, 
    "arguments", allowing declaration of both predicate argument names and 
    predicate argument descriptions. Added new info/2 documenting directive
    key, "examples", allowing the representation of predicate call examples.

    Much improved and accurate reporting of non-portable predicate calls when 
    using the "portability" flag.

    Added a new directory to the Logtalk distribution, "contributions", which 
    will be used for user-contributed code. On this release, it contains an 
    implementation of the ISO 8601 standard by Daniel L. Dudley, providing a 
    library of useful date predicates.

    Added new lgt2xml.* shell scripts for generating (X)HTML indexes of XML 
    documenting files.

    Rewritten the lgtxhtml.xsl, lgthtml.xsl, lgtxml.xsl XSLT scripts in order 
    to make it easier to define alternative CSS files for the generated HTML 
    files. Rewritten the lgtpdfa4.xsl and lgtpdfus.xsl XSLT scripts in order 
    to improve appearance of the generated PDF files.

    Improved the documentation of the "benchmarks" example and added new 
    predicates for running batches of benchmark tests and for generating 
    lists of known size for the benchmark tests of static code.

    Corrected a bug in the lgt2html.*, lgt2pdf.*, and cplgtdirs.sh shell 
    scripts which resulted in failed transformations whenever the LOGTALKHOME 
    and LOGTALKUSER environment variables or the output directory contained 
    spaces or accented characters.

    Added workaround for Prolog compilers that define operators other than 
    ','/2 that cannot be redefined (such as new B-Prolog 6.7).

    Added a Logtalk "clip" file for the TextPad Windows text editor.

    Renamed directory "misc" to the more meaningful name "scripts".

    Corrected a bug in the implementation of the built-in database methods 
    asserta/1 and assertz/1 when asserting facts on objects compiled in debug 
    mode.

    Corrected a bug in the method leash/1 of the built-in pseudo-object 
    "debugger", which failed to accept an empty list as a valid argument.

    Corrected a bug in the header of the automatically generated XML 
    documenting files when using the XML Schema specification (logtalk.xsd), 
    which could prevented validation when the compiler flag "doctype" is set 
    to "web".

    Corrected a compilation bug where Prolog clauses written outside entities 
    on source metafiles would have their order reversed. Simplified splitting 
    of source metafiles.

    Corrected a compilation bug where Prolog clauses written before an entity 
    opening directive would not be copied to the generated Prolog file.

    Corrected a bug on the "roots" example in the object "class" which failed 
    to properly test the validity of new object identifiers.

    Corrected a bug in the syntax coloring file for the Vim text editor, which
    resulted in an error message when opening a Logtalk source file for the 
    first time.


2.23.1 - March 7, 2005

    Simplified message sending compilation, improving performance of both 
    entity compilation and runtime top-level message sending.

    Simplified implementation and improved performance of the built-in method 
    current_predicate/2.

    Updated the runtime error handler for top-level ::/2 calls to recognize 
    non-existing predicate exceptions thrown by XSB, SICStus Prolog, CIAO, 
    B-Prolog, and recent development versions of SWI-Prolog. Rewritten the 
    ::/2 predicate in order to minimize the overhead of the catch/3 calls 
    associated with the runtime error handler, thus improving performance.

    Expanded the benchmarks example to test performance of the built-in 
    database methods.

    Lookup caches are now cleaned before loading a redefined entity in order 
    to avoid potential problems with entity initialization goals containing 
    message sending calls (previous versions cleaned the caches only after 
    entity loading).

    When reloading an object, its tables of dynamic predicate declarations 
    and dynamic predicate definitions are now reseted.

    Corrected a compatibility problem with the "birds" example due to the use 
    of an operator not available in some Prolog compilers.


2.23.0 - February 21, 2005

    Optimized the code generated for local calls to the built-in predicates 
    asserta/1, assertz/1, retract/1, and retractall/1, when the argument is 
    a dynamic predicate declared by a scope directive in the object making 
    the calls.

    Added caching of predicate compiled forms for dynamic facts when used 
    with the database built-in methods clause/2, asserta/1, assertz/1, 
    retract/1, and retractall/1, resulting in a significant performance 
    improvement when using an object's dynamic database. Improved performance 
    of the database built-in methods abolish/1, asserta/1, assertz/1, clause/2, 
    retract/1, and retractall/1 when the cache is not used.

    Corrected a bug on the implementation of the built-in methods asserta/1 
    and assertz/1 that prevented asserting of rules.

    Corrected a bug on the implementation of built-in methods retractall/1, 
    retract/1, and clause/2 that allowed access to local dynamic predicates 
    from outside the container object.

    Added a runtime error handler for top-level ::/2 calls which tries to deal
    with exceptions thrown by calling non-existing predicates by translating 
    Logtalk generated internal predicate names to user names.

    Print the total number of warnings after a call to the Logtalk built-in 
    predicates logtalk_compile/1-2 and logtalk_load/1-2.


2.22.5 - February 9, 2005

    Added scripts for easy integration of Logtalk with K-Prolog. Updated the 
    K-Prolog config file, correcting a show-stopper bug and enabling support 
    for using the "library" notation for loading source files.

    Updated JIProlog config file in order to allow smart compilation of source
    files.

    Changed format of preprocessor and runtime dynamic predicates that deal 
    with predicate indicators for better performance.

    Simplified implementation of Logtalk built-in methods asserta/1 and 
    assertz/1.

    Corrected a performance bug with calls to built-in predicates from objects
    and categories.

    Corrected spurious backtracking occurring on some calls to the built-in 
    predicate define_events/5.

    Updated shell script "misc/cplgtdirs.sh" to prevent copy of Logtalk files 
    when the destination directory already exists (thus avoiding overriding 
    any user-modified files when upgrading Logtalk).

    Added syntax coloring for the predicate logtalk_library_path/2 to the 
    supported text editors. Updated the syntax coloring file for the TextMate 
    text editor, adding some missing ISO Prolog predicates.

    Improved printing of lists of unknown referenced entities, misspelt calls,
    and singleton variables when compiling source files. Simplified handling 
    of references to unknown entities.

    Added workaround for Prolog compilers with broken read_term/3 singletons/1
    option.

    Updated the Logtalk compiler/runtime and the documentation to always 
    use the expression "compiler flag" instead of "compiler option" for 
    consistency. Other minor documentation improvements.

    Corrected a bug with the abolishing of dynamic entities where the clauses 
    corresponding to the alias/3 directive are not being abolished.

    Added new predicates '$lgt_call'/9 and '$lgt_once'/9 to all config files.

    Simplified and improved performance of compilation of directives containing
    predicate indicators.


2.22.4 - January 12, 2005

    Simplified method lookup cache tables, resulting in a small message 
    sending performance speedup. Improved method lookup caching for 
    parametric objects. Added support for caching method lookups for 
    parametric objects whose parameters contain cyclic terms.

    Added a new category, "assignvars", to the Logtalk standard library, 
    containing an adaptation of the implementation of logical assignable 
    variables developed by Nobukuni Kino. Added a new example, "assignvars",
    illustrating some possible uses of assignable variables in the context 
    of parametric objects.

    Simplified compilation of op/3 directives: there is no longer need to 
    repeat the directives both before and inside an entity in order to make 
    the operators global and also use them in the compilation process.

    Simplified installation instructions.

    Corrected a compiler bug in the code that checks and prints a warning 
    when redefined parametric objects.

    Corrected a bug in the built-in predicate abolish_category/1, which 
    failed to delete import relation clauses between the category being 
    abolished and other categories.


2.22.3 - December 30, 2004

    Added a configuration file for XSB 2.7.

    Corrected a bug where the use of alternative compilation directories 
    would fail the first time the logtalk_compile/1-2 or logtalk_load/1-2 
    predicates are used for a given file or library.

    Corrected a bug in the built-in methods asserta/1 and assertz/1 when 
    asserting facts into an object being debugged, which resulted in wrong 
    execution context information being printed when tracing calls to 
    the asserted facts.

    Corrected a bug in the built-in methods asserta/1 and assertz/1 when 
    asserting rules into an object being debugged, which resulted in rule 
    bodies compiled with no information being printed for the rule head 
    when tracing calls to the asserted rules.

    Corrected a bug in the dynamic creation of objects, protocols, and 
    categories when the debug flag is on, which resulted in the table of 
    entities being debugged not being updated.

    Corrected a bug in the handling of exceptions thrown when using the 
    built-in debugger, which resulted in exceptions always being turned 
    into failures.


2.22.2 - December 24, 2004

    Improved performance of dynamic creation and compilation of objects, 
    protocols, and categories.

    Improved error-checking code of methods asserta/1 and assertz/1 to 
    prevent asserting of non-callable terms as facts.

    Improved error checking for documenting directives (info/1 and info/2).

    Improved the XSB integration script (make_xsblgt.sh) in order to use the 
    configuration file and the libpaths file available from the $LOGTALKUSER 
    directory.

    Improved installation instructions and installation scripts documentation.

    Added documentation to the user manual on describing predicate exceptions 
    using the info/2 directive.

    Corrected a bug in the predicate_property/2 built-in method when called 
    with the second argument instantiated to the alias/1 property.


2.22.1 - December 6, 2004

    Improved installation instructions. Updated the Windows installation 
    JScript script to add the Logtalk directories "misc" and "xml" to the 
    system PATH environment variable and to reuse the environment variable 
    LOGTALKUSER if already defined.

    Added helper batch scripts (misc/cplgtdirs.bat, xml/lgt2html.bat, and 
    xml/lgt2pdf.bat) for easily running the corresponding Windows JScript 
    scripts from the command-line (the two xml/lgt2*.bat scripts run the 
    corresponding *.js scripts stored in the %LOGTALKUSER%/xml directory 
    in order to support user customization).

    Updated the lgt2html.* and lgt2pdf.* shell scripts to use the environment 
    variable LOGTALKUSER instead of LOGTALKHOME for finding supporting files, 
    thus allowing for end-user customization of the scripts and their related 
    files.

    Added documentation on read-only compiler flags (which are defined in the 
    configuration files) to the User Manual.

    Updated the misc/lgt_install.js JScript installer script to workaround a 
    Windows Scripting Host bug which may result in broken shortcuts in the 
    created "Logtalk" program group.


2.22.0 - November 29, 2004

    Implemented a notion of library as simply a directory containing source 
    files. Added a new dynamic predicate, logtalk_library_path/2, for 
    specifying library paths. Added a sample file (libpaths/libpaths.pl) for 
    setting library paths for the Logtalk standard library and for all the 
    supplied examples.

    Added support for using the notation <library>(<entity>) with the built-in
    predicates logtalk_compile/1-2 and logtalk_load/1-2 for compiling and 
    loading source files contained on a library, without the need to first 
    change the current working directory.

    Changed the library and the examples loading instructions to use the new 
    notation <library>(<entity>).

    Improved installation instructions and installation scripts. Added a new 
    environment variable, LOGTALKUSER, for defining the location of the copies 
    of the user-modifiable Logtalk files in a multiple users setup environment.

    Added utility predicates to most configuration files for querying and 
    changing the current working directory (needed for the <library>(<entity>) 
    notation to work).

    Corrected a bug in the code that checks for file existence when compiling 
    or loading source files and source metafiles.


2.21.6 - November 15, 2004

    Added support for using alternative directories for storing the Prolog files 
    and the XML documenting files resulting from entity compilation. A new read-
    only flag, "altdirs", allows the support for alternative directories to be 
    turned on the configuration files of Prolog compilers providing the necessary 
    operating-system access predicates for implementing this feature.

    Improved installation instructions and reporting of default compilation flags 
    at startup.

    Added a sorely missing "Hello World!" example :-)


2.21.5 - November 2, 2004

    Added a new optimization compiler flag, "events", which can be used to switch 
    off event-driven programming support when not needed, on a per-object basis, 
    resulting in improved message sending performance.

    Small performance optimization to the runtime creation of dynamic objects, 
    protocols, and categories.

    Updated the error handling code of the built-in predicates create_object/4, 
    create_protocol/3, and create_category/4 in order to throw an instantiation 
    error when called with a non-instantiated argument.

    Updated the benchmarks example to calculate and subtract the benchmark loop 
    time in order to print absolute timings for the benchmarked goals.

    Updated the Qu-Prolog patching instructions to also convert Logtalk source 
    metafiles.

    Fixed a typo on the XSB compatibility notes in the configs/NOTES file.


2.21.4 - October 26, 2004

    Corrected a silly bug in the definition of the predicate repeat/1 on the 
    new "benchmarks" example.


2.21.3 - October 25, 2004

    Corrected a silly bug in message translation which resulted in a small 
    performance loss. Simplified implementation of message sending predicate 
    ::/2, resulting in a small performance improvement.

    Added a new section on message sending performance to the user manual.

    Added a new example, "benchmarks", for helping measuring performance of 
    Logtalk message sending between Prolog compilers and for comparing message 
    sending with predicate calls in plain Prolog and with calls to modules 
    predicates.

    Updated the YAP configuration file to hide some of the book-keeping tables 
    of the Logtalk runtime engine and to use statistics/2 instead of cputime/0 
    for more accurate timings.

    Updated the Logtalk shell installation script to create the $prefix/bin 
    directory if it does not exist.

    The lgt2pdf.sh and lgt2html.sh shell scripts now use "rm -f" when removing 
    the DTD and XSD files in order to avoid prompting the the user about the file 
    permissions.

    Updated the cplgtdirs.sh shell script to make all copied files user writable.


2.21.2 - October 18, 2004

    Added support for declaring grammar rule non-terminals as public, protected, 
    private, dynamic, or discontiguous using the notation Functor//Arity. Added 
    support for documenting non-terminals using the info/2 and mode/2 directives.

    Added support for a new alias/1 predicate property.

    New experimental config file for JIProlog 3.0 (see the configs/NOTES file 
    for details).

    Added a mode bundle for the TextMode 1.0.x (MacOS X) text editor providing 
    syntax highlighting, folding, and code snippets for editing Logtalk source 
    files. Corrected a bug in the syntax coloring of the :-/1-2 operator on the 
    SubEthaEdit 2.x text editor.


2.21.1 - September 27, 2004

    Added experimental support for a new built-in method, expand_term/2, which 
    allows access to the Logtalk grammar rule translator. Corrected bug in the 
    expansion of \+/1 in grammar rule bodies. Optimized code generated for 
    message sending calls in the body of grammar rules. Improved error handling 
    of the built-in methods phrase/2 and phrase/3. Added new section on definite 
    clause grammars to the user manual. Added two new objects to the "dcgs" 
    example, dcgtest and bypass, containing test cases for the Logtalk DCG 
    translator and illustrating some programming techniques with grammar rules.

    Corrected a bug in the implementation of the built-in method clause/2 which 
    prevented access to clauses of local dynamic predicates.

    Corrected some dead links on the XHTML manuals.

    Corrected a bug in the syntax coloring of numbers on the SubEthaEdit 2.x 
    text editor.


2.21.0 - September 14, 2004

    Added a new predicate directive, alias/3, which allows the definition of 
    alternative predicate names in order to improve readability of inherited 
    features and to solve conflicts between implemented, imported, or inherited 
    predicates.

    Added new example, "aliases", illustrating the use of the new alias/3 
    predicate directive for improving readability of inherited features.

    Added new example, "diamonds", illustrating problems and solutions for the 
    "diamond problem" (multi-inheritance conflicts and ambiguities) using the 
    new alias/3 predicate directive.

    Allow categories to import other categories, i.e. allow categories to be 
    defined as a composition of other categories. This feature should only be 
    used when extending a category without breaking its functional cohesion 
    (for example, when a modified version of a category is needed for importing 
    into several unrelated objects). 

    Added new example, "engines", illustrating importing a category from another 
    category.

    Updated the syntax coloring configuration files for the supported text 
    editors for the new alias/3 predicate directive.

    Added auto-complete strings for Logtalk methods and for Logtalk and Prolog 
    built-in predicates and directives to the SubEthaEdit 2.x text editor.

    Corrected a bug which prevented compilation of metafiles containing 
    parametric entities.


2.20.2 - August 31, 2004

    Added a Windows JScript script for installing Logtalk. Improved the Windows 
    JScript scripts used for easy integration of Logtalk with selected Prolog 
    compilers.

    Improved user manual section on defining object and category metapredicates 
    and on calling non-standard Prolog built-in metapredicates. Improved the 
    description of some compiler options.

    Added some files missing from the "errors" example (which should have been 
    included in the previous release).

    Added basic syntax coloring support for the BBEdit 8.x text editor.


2.20.1 - August 19, 2004

    Added Windows JScript scripts for easy integration of Logtalk with CIAO and 
    GNU Prolog.

    Added encoding attribute (set to UTF-8) to the xsl:output tag in the 
    lgtxml.xsl, lgthtml.xsl, and lgtxhtml.xsl files.

    Replaced the Windows JScript scripts lgt2pdf.js and lgt2html.js by their 
    final versions (the wrong ones shipped with Logtalk version 2.20.0).

    Updated the "errors" example to illustrate possible conflict errors when 
    using the uses/2 directive.

    Updated the RPM logtalk.spec file to use the .tgz archive extension.


2.20.0 - August 16, 2004

    Added support for the uses/2 predicate directive (whose semantics is similar 
    to C++ using-declarations). Updated the uses/1 entity directive to accept as 
    argument a single object identifier.

    Improved installation instructions for Windows users.

    Added four new sample bash shell scripts and Windows JScript scripts for 
    converting XML documenting files to PDF, HTML, and XHTML using several XSL 
    processors.

    Added missing namespace to XSL files in order to generated valid (X)HTML 
    files with recent versions of XSLT processors.

    Updated the User Manual documentation on converting XML documenting files 
    to other formats.

    Removed the texml.xsl XSLT file as the TeXMLatte application it depends on 
    is no longer available.

    Added Windows JScript script for copying the Logtalk examples, library, and 
    xml directories to the user directory.

    Added Windows JScript scripts for easy integration of Logtalk with ECLiPSe, 
    SWI-Prolog, SICStus Prolog, and YAP.

    Added missing extension for source metafiles to the SWI-Prolog hook file.
    
    Corrected a bug in the lgtxhtml.xsl XSLT file where a wrong reference to 
    the Logtalk CSS file is being used in the xml-stylesheet tag.

    The iso_initialization_dir/1 compiler option is now a read only flag, 
    defined in the configuration files.


2.19.1 - August 2, 2004

    Corrected a bug where entities could not be reloaded if they depend on 
    other, not yet loaded entities.

    Corrected a bug where compiler options would not be used when compiling 
    source metafiles.

    Corrected several typos on the Logtalk manuals.


2.19.0 - July 26, 2004

    Added support for defining more than one entity per file using Logtalk 
    source metafiles (*.mlgt), which the runtime engine automatically splits 
    on single entity source files plus loading and compiling helper files.

    Updated the URL used on the automatically generated XML documenting files 
    when compiling entities with the option doctype(web).

    Improved error checking when compiling calls to the {}/1 control construct.

    Corrected several typos and some outdated links on the Logtalk manuals.


2.18.0 - July 9, 2004

    Added caching of method lookups in order to improve message processing 
    performance (including messages to self and super calls). Applied several 
    optimizations to runtime translation of messages in order to further 
    improve performance.

    Improved error checking while parsing and compiling messages to self.

    Update ECLiPSe config files to compile the Prolog files generated by Logtalk 
    (when compiling source files) in optimized mode instead of traceable mode.

    Updated description of patches needed for running Logtalk with XSB, added 
    a shell script for easy integration of Logtalk with this Prolog compiler, 
    and corrected a problem with its corresponding config file.

    Added multifile/1 directive to the syntax coloring configuration files of the 
    supported text editors.


2.17.2 - June 14, 2004

    Updated the Logtalk compiler to allow compilation of source files which 
    contain only directives and no entity definition.

    Simplified loading of library and example entities by using Logtalk source 
    files as loader files.

    Some improvements to the documentation, including the QUICK_START file and 
    the User Manual for first-time users, and to the example descriptions.

    Corrected a bug in handling of local object operators that are also global 
    operators.

    Corrected a bug where dynamic directives are not being generated for dynamic 
    predicates that lack a scope directive or an initial set of clauses.

    Corrected a bug where local dynamic predicates would need a private scope 
    directive in order to allow clauses of the predicate to be retracted.

    Simplified compilation of dynamic and discontiguous predicate directives.

    Added new "logic" example implementing a translator from logic propositions 
    to conjunctive normal form.

    Corrected a problem with wrong end-on-lines on some files.

    Added a shell script for easy integration of Logtalk with CIAO Prolog.


2.17.1 - June 7, 2004

    Added custom handling of specification of predicate exceptions in info/2 
    documenting directives when writing XML documenting files (declared as 
    "exceptions is [Cond1-Term1, Cond2-Term2, ...]"; each pair (Condi, Termi) 
    represents an error condition and its respective exception). 

    Changed debugger command "e" to print exception terms instead of exiting 
    Logtalk session.

    Corrected a compilation error with B-Prolog due to operator priorities.

    Corrected a possible problem with the redefinition of loaded entities that 
    define (possibly at runtime) dynamic predicates. All clauses for an entity 
    dynamic predicates are retracted before loading the new entity definition.

    Corrected a potential bug when pretty printing terms with variables in the 
    debugger and in the created XML documenting files.

    Added four more DCGs examples ("walker movements", "iterative shell command 
    parsing", "bill of materials", and "command language").
    
    New "puzzles" and "metainterpreters" examples.

    Added a mode bundle for the SubEthaEdit 2.x (MacOS X) text editor providing 
    syntax coloring for editing Logtalk source files. Optimized some of the 
    regular expressions in the syntax coloring files for the Kate/Kwrite and Vim 
    text editors.

    Removed predicate nth/3 from library entities listp, list, and difflist. 
    Replaced by the predicates nth0/3 and nth1/3. Added new predicates nth1/4 
    and nth0/4.

    Updated the config file for Quintus Prolog to make use of the "files" 
    library.

    Added experimental implementations for some Prolog compilers of the library 
    portable protocol for operating system access (systemp.lgt). See the file 
    library/experimental/NOTES for details.


2.17.0 - April 26, 2004

    Added built-in debugging support implemented through the definition of a 
    new pseudo-object named "debugger". Added "debug" compiler option. Renamed 
    library entities "debuggerp" and "debugger" to, respectively, "event_dbgp" 
    and "event_dbg".

    Improved installation instructions for multi-user environments. Added 
    a shell script for installing Logtalk in Unix and Unix-like operating 
    systems. Added a shell script for copying Logtalk xml, examples, and 
    library directories to the user home directory.

    Added a logtalk.spec file for building Linux RPMs from sources.

    Added a set of shell scripts for easy integration of Logtalk with ECLiPSe, 
    GNU Prolog, Qu-Prolog, SICStus Prolog, SWI-Prolog, and YAP.

    Corrected bug in the definition of the pseudo-object "user" that resulted 
    in mixed up metapredicate and type predicate properties.

    Removed config files for outdated versions of Qu-Prolog, SWI-Prolog, ECLiPSe,
    K-Prolog, CIAO, YAP, Amzi! Prolog, LPA Win-Prolog, SICStus Prolog, and XSB.


2.16.2 - April 2, 2004

    Corrected a bug in the library category monitor (file library/monitor.lgt) 
    that prevents its compilation.

    Changed the possible values of the read-only flag startup_message (defined 
    in the config files) to "flags" (print banner and flag values), "banner" 
    (print only the banner), and "none" (do not print neither the banner nor the 
    flag values). Default value is "flags".

    Updated the "errors" example to illustrate the error messages thrown when 
    trying to redefine Logtalk built-in control constructs.

    Corrected a small problem with the Logtalk language specification file for 
    Apple's Xcode IDE.

    Added preliminary support for syntax coloring using the Windows text editor 
    Crimson Editor.


2.16.1 - March 23, 2004

    The local built-in method parameter/2 can now be used inside categories 
    (but please read the warnings about such practice on the user manual).

    Updated the Logtalk compiler to report an error when the user tries to 
    redefine a message sending or external call control construct inside an 
    object or category.

    Corrected a bug in the compilation of metacalls whose meta-arguments are 
    variables.

    Removed references to file sax.jar from the scripts used to convert XML 
    documenting files into (X)HTML. Updated scripts html.sh, htmlnt.cmd, and 
    htmldos.bat to use XT 20020426a or later version.

    Improved syntax coloring accuracy of built-in predicates and methods for 
    the SubEthaEdit text editor.

    Updated config file for Qu-Prolog 6.4.


2.16.0 - March 3, 2004

    Logtalk is now distributed under the Artistic License 2.0.

    Operators declared inside an entity are now local to the entity, not 
    affecting the global operator table (complying with the Logtalk language 
    specification). Input and output of terms from inside objects and 
    categories now work as expected in the presence of local operator 
    declarations. Added a new example named "operators".

    Updated built-in method predicate_property/2 for returning metapredicate/1 
    properties for both Logtalk and Prolog metapredicates.

    Added support for calls to non-ISO Prolog standard built-in metapredicates 
    inside objects and categories. Added support for the declaration of non-ISO 
    Prolog standard metapredicates in the config files.

    Small change to the way the Logtalk compiler reports the compilation of
    entities. Small optimizations to the compilation of Logtalk source files.

    Corrected a bug where calls to Logtalk built-in predicates would be 
    reported as non-portable when the value of compiler option portability is 
    set to warning.

    New config file for Qu-Prolog 6.4 (see the configs/NOTES file for details).

    Corrected a problem with the syntax coloring of quoted atoms and strings 
    in the SubEthaEdit text editor. Added more accurate syntax highlight for
    built-in methods and built-in predicates.

    Updated the syntax coloring configuration files for all supported text 
    editors to recognize the file extension used by the config files.


2.15.6 - February 9, 2004

    Added "xmlspec" compiler option in order to specify the extension (dtd 
    or xsd) of the file describing the XML documenting files specification.

    Renamed compiler option "named_anonymous_vars" to the more appropriated 
    name "underscore_vars". Changed possible option values to "dont_care" and 
    "singletons" (default).

    Added XSLT file for converting XML documenting files to XHTML 1.0 Strict 
    files. Set the default encoding of all XSLT files to UTF-8.

    Added syntax coloring support for the KDE Kate and Kwrite text editors.

    Improved syntax coloring configuration files for VIM, jEdit, NEdit, 
    SubEthaEdit, and Emacs text editors.

    Removed outdated support for MacOS X Project Builder and added support 
    for the new MacOS X Xcode developer tool.

    Corrected bug in the built-in predicate current_logtalk_flag/2 that 
    prevented some flag values from being returned after using the built-in 
    predicate set_logtalk_flag/2.

    Corrected bug in the shapes example (wrong placement of the declaration 
    of the predicate side/1).


2.15.5 - December 30, 2003

    Make operator ^^/1 right-associative for consistency with remaining 
    operator declarations.

    Added file BIBLIOGRAPHY containing a list of Logtalk publications in 
    BibTeX format.

    Added a font-lock file for Emacs providing syntax coloring for editing 
    Logtalk source files.

    Added an implementation of the Smalltalk dependent mechanism to the 
    standard Logtalk library.

    Updated the config file for ECLiPSe 5.4~5.7 with missing ISO Prolog 
    predicate definitions needed for successful compilation of all entities 
    in the Logtalk standard library.

    Updated manual pages to comply with XHTML 1.0 Strict and to provide 
    better navigation.


2.15.4 - July 9, 2003

    Corrected a spurious backtracking bug in the DCG rule translator. Added 
    two more examples of DCGs.

    New config file for XSB 2.6. Updated Logtalk compiler to compile cleanly 
    under XSB after applying the patch described in configs/NOTES.

    Updated SWI-Prolog config file to hide compiled entity predicates (requires 
    SWI-Prolog 5.2.3 or later version). New optional file configs/swihook.pl 
    contains hook code that allows Logtalk entities to be compiled and loaded 
    using SWI-Prolog load_files/2 and consult/1 predicates.

    Syntax definition file for the Hydra 1.1 (MacOS X) text editor providing 
    syntax coloring for editing Logtalk source files.

    Updated syntax coloring files for jEdit, NEdit, Vim, and TextPad in order 
    to recognize character code constants (0'x) and the DCG operator -->/2.


2.15.3 - June 27, 2003

    Updated experimental support for DCG rules to prevent over-simplification 
    of unification goals in the compilation of rules to clauses. Push-back 
    lists can now be used on rule heads.

    The compilation mode of an entity (static/dynamic) is now stored in the 
    corresponding entity table (implying recompilation of all entities).

    Updated GNU Prolog config file to hide compiled entity predicates.

    Updated SWI-Prolog config file for better integration of Logtalk with 
    this compiler.


2.15.2 - April 2, 2003

    Experimental support for DCG rules inside categories and objects. Added 
    built-in methods phrase/2 and phrase/3.

    Updated GNU Prolog config file to not hide compiled entity predicates in 
    order to avoid incompatibilities with dynamic entities.


2.15.1 - March 8, 2003

    New example, msglog, of using events and monitors to record, replay, and 
    print user messages.

    Corrected a typo on the jEdit templates that resulted in syntax errors.
    Corrected wrong year format in info/1 directive in all entity templates.
    Added missing version info key to jEdit prototype template.

    Corrected documentation of built-in local methods self/1 and sender/1.
    Updated documentation of built-in local methods parameter/2 and this/1.


2.15.0 - February 5, 2003

    Changed "authors" key in info/1 directive to "author".

    Corrected documentation of built-in local method this/1.

    New geometric shapes example implemented in two versions, one 
    prototype-based and the other one class-based.

    Improved support for jEdit text editor by adding a set of programming 
    templates for use with the editor Templates plug-in.

    Added basic support for syntax highlighting and programming templates 
    for MacOS X Project builder.


2.14.7 - January 10, 2003

    Corrected a bug in the built-in methods asserta/1 and assertz/1 when 
    asserting predicate rules.

    The built-in predicates logtalk_compile/1-2 and logtalk_load/1-2 now 
    accept both an entity (an atom) or a list of entities (a list of atoms).

    Optimized the code generated when compiling or asserting clauses for 
    dynamic predicates.

    Optimized protected inheritance performance on some Prolog compilers.


2.14.6 - December 31, 2002

    Corrected a bug where the opening directive of an object that, 
    simultaneously, implements a protocol, imports a category, instantiates 
    a class, and specializes a superclass, will not be recognized.


2.14.5 - December 20, 2002

    Simplified dynamic table of predicate declarations by removing two 
    redundant arguments.
    
    Corrected a bug where sending messages such as true/0 or !/0 to an 
    unknown object succeeded instead of throwing the correct exception.

    Simplified the code used to generate links in the lgtpdfa4.xsl and 
    lgtpdfus.xsl XSLT files.


2.14.4 - November 5, 2002

    Removed definition of deprecated built-in predicate logtalk_version/3.

    Show flag names when printing at startup the default flag values.

    Small change to messages printed on console with smart compilation of 
    source files turned on.

    Updated YAP 4.3.x config file to use the YAP "system" library to access 
    the operating system for time, date, and file properties (enabling smart 
    source code compilation).

    Updated the lgtpdfa4.xsl and lgtpdfus.xsl XSLT files to workaround a bug 
    in the PassiveTeX 1.21 XSL:FO processor.


2.14.3 - September 16, 2002

    New compiler option, doctype, to set the doctype reference (if any) 
    in the XML documenting files. Default value is "local" for backward 
    compatibility. Updated the user manual section on compiler options.

    The Logtalk built-in predicate logtalk_version/3 should be considered 
    deprecated (use current_logtalk_flag/3 instead). All references to this 
    predicate have been removed from the manuals.

    Updated the jEdit syntax coloring config file for the new jEdit 4.1 
    version.

    Updated the lgtpdfa4.xsl and lgtpdfus.xsl XSLT files for compatibility 
    with the XSL:FO processors Apache FOP 0.20.4, PassiveTeX, and RenderX 
    and with the XSL W3C Recommendation of October 15, 2001. Updated the 
    pdf.bat and pdf.sh scripts to reference the latest version of the 
    Apache FOP processor (0.20.4).

    Changed the shell scripts html.sh and pdf.sh for compatibility with the 
    sh, bash, and zsh shells.


2.14.2 - August 26, 2002

    Calls to built-in method parameter/2 are now compiled inline, improving 
    call performance.

    Updated Logtalk compiler to clean temporary compilation predicates after 
    compiling an entity instead of only before compilation.

    Updated YAP 4.3.x config file for better Logtalk integration by hiding 
    all internal compiler, runtime, and compiled entities static predicates.

    Updated GNU Prolog config file for better Logtalk integration by hiding 
    all internal compiler, runtime, and compiled entities predicates.

    Updated the XSLT conversion scripts lgtxml.xsl and lgthtml.xsl to correct 
    some HTML conformance errors in the generated pages.

    Corrected some XHTML conformance errors in the manual pages.


2.14.1 - July 31, 2002

    New Windows NT script and updated Unix shell script for batch converting 
    XML documenting files to HTML. Both scripts also generate an index.html 
    file containing links to all converted XML documenting files.

    Corrected wrong XHTML DOCTYPE declaration in manual pages.


2.14.0 - July 26, 2002

    Renamed all compiler and runtime internal predicates and all auxiliary 
    predicates in the config files to start with a "$" character.
    
    New compiler option, code_prefix, to set a prefix for all Prolog code 
    functors generated by Logtalk when compiling entities. Default is ''.

    New compiler option, named_anonymous_vars, that instructs the compiler to 
    interpret variables that start with an underscore as anonymous variables 
    (and to not report them as singleton variables). Default value is "off".

    Directive info/2 was wrongly declared as a entity directive instead of a 
    predicate directive.

    Converted all manual pages to XHTML 1.0 format. Corrected a wrong link in 
    the reference manual. Replaced GIF images by PNG versions.

    Updated BProlog 6.x config file to workaround the new 6.2 built-in 
    predicate ::/2 that conflicts with the same named Logtalk message sending 
    operator.

    Removed call to the obsolete built-in predicate nodbgcomp/0 from all 
    ECLiPSe config files.


2.13.0 - June 15, 2002

    Logtalk now outputs Prolog code using write_canonical/2 instead of 
    write_term/3. Goals are better portability of the generated Prolog files 
    and avoid issues with clauses with long bodies for Prolog compilers that 
    use a term print depth limit to prevent problems with cyclic terms.

    Added report of default flag values at Logtalk startup.

    Logtalk now prints a warning when redefining parametric objects.

    Removed need of an abort/0 predicate from the Logtalk debugger example.
    Removed any definition of this predicate from the config files.

    Added missing definitions for some ISO built-in predicates to the Amzi! 
    Prolog 6.2.2 config file.


2.12.0 - May 25, 2002

    New read-only Logtalk flag "version". Corrected exception term generated 
    when trying to modify a read-only flag using the set_logtalk_flag/2 
    built-in predicate.

    Updated config file for OpenProlog 1.1b5.

    New config file for ECLiPSe 5.4.

    Renamed config files for CIAO 1.7 (beta of 1.8) to "ciao_aux18.config" 
    and "ciao18.config".

    Updated config file for Amzi! Prolog 6.2.2.

    New example of using some of the built-in database handling methods 
    (dynpred).

    Syntax configuration files for jEdit 4.0, VIM 6.1, NEdit 5.2, and 
    TextPad 4.5 text editors providing syntax highlighting for editing 
    Logtalk source files.


2.11.0 - April 22, 2002

    Added a "smart compilation" feature to the Logtalk compiler, controlled 
    by a "smart_compilation" flag. Only available in Prolog compilers that 
    provide access to file modification dates.

    Added a "startup_message" flag to control printing of the Logtalk banner 
    at startup.

    Reworked Logtalk pre-processor compilation and loading reports. Compiler 
    option "report" now toggles between normal reporting (as specified by the 
    other flags) and silent compilation/loading of source files.


2.10.0 - April 5, 2002

    Scope of object asserted predicates for which there is no declaration is 
    now a function of the context instead of always being declared public. 
    Asserting in this, the predicate is declared private, asserting in self, 
    the predicate is declared protected, otherwise the predicate is declared 
    public.

    Throw an error if a category contains clauses for dynamic predicates.

    Updated documentation on categories and built-in methods for database 
    handling.

    Retracting all clauses for a dynamic predicate from an object now allows 
    an inherited definition to be called when sending the corresponding 
    message. In previous versions the message just failed.

    Added missing entries for the built-in predicates current_logtalk_flag/2 
    and set_logtalk_flag/2 to the Logtalk compiler built-in predicates table.

    Updated config file for Amzi! Prolog 6.1.74.

    Updated notes on patching XSB to work with Logtalk.


2.9.3 - February 9, 2002

    New current_logtalk_flag/2 and set_logtalk_flag/2 built-in predicates.

    Updated documentation on new built-in predicates.

    Renamed SWI-Prolog config file swi330.config to swi.config.

    Renamed config file predicate lgt_default_compiler_option/2 to lgt_flag/2.

    New XSL style-sheets and shell scripts to convert Logtalk XML entity 
    documenting files to PDF format using XSL Formating Objects.


2.9.2 - January 4, 2002

    The Logtalk compiler can now print a warning when compiling source files 
    that use non-ISO defined built-in predicates using a new portability/1 
    compiler option. Updated the relevant sections of the user manual and the 
    errors example.

    Corrected a compiler bug where the entity relation tables only recorded 
    the last entry per entity relation type.
    
    Updated config file for CIAO 1.7#162.


2.9.1 - December 5, 2001

    Logtalk compiler now prints a warning when redefining or replacing an
    existing entity.

    Corrected a compiler bug in the error checking code for the info/1 
    and info/2 directives.

    Changed the order of object loading in the "mi" example to avoid 
    spurious warning messages.
    
    Added a new problem ("bridge") to the "searching" example. Improved 
    "performance" monitor to give correct reports on alternative solutions. 
    Corrected a bug in the "water jug" state space example.


2.9.0 - October 22, 2001

    Added config files for CIAO Prolog 1.7p115 and B-Prolog 6.0.

    Compiling and loading an entity that contains references to unknown 
    entities (by default) prints a warning. Updated user and reference 
    manuals.

    Rewritten all the compiler warning/error code and output messages.

    Changed compiled code functors postfixes from "_sdcl" and "_sdef" to 
    "_idcl"    and "_idef" (implies recompilation of all objects, protocols, 
    and categories).

    Changed all occurrences and references to the term "entity_scope" to 
    "scope".

    Removed some redundant productions from the Logtalk grammar.

    Updated documentation on the xml directory. Renamed some of the .xsl 
    files. Added sample scripts to batch convert .xml files to .html files.
    
    Added a new loader utility file, all.loader, to load all library files 
    loaded by the other loader files.

    Started work on documenting the Logtalk pre-processor/compiler source 
    file.

    New "errors" example. Updated the "inheritance" example.


2.8.4 - March 9, 2001

    Updated config files for BinProlog 8.0, K-Prolog 5.01, XSB 2.3, and
    Amzi! Prolog 4.103~5.0.
    
    New config file for Amzi! Prolog 6.1 beta.

    Corrected an incomplete entity definition in the Logtalk XML DTD.
    Rewrite the Logtalk XSLT files for improved compatibility with XSLT 
    processors regarding handling of whitespace.

    A first cut of a XML Schema for the Logtalk XML documentation files
    (file xml/logtalk.xsd).

    Small improvements to the documentation.


2.8.3 - November 21, 2000

    Corrected a bug where sending a message for a built-in method to an 
    unknown object fails instead of generating the expected exception.

    Put some occurrences of atoms public, mode, and type between ()'s to 
    avoid compilation errors in BinProlog 8.0 and other Prolog compilers 
    that declare these atoms as operators.

    Corrected the definition of the state space of the "Missionaries and 
    Cannibals" problem in the "searching" example that resulted in some 
    wrong solutions.


2.8.2 - November 5, 2000

    New .xsl file to convert .xml files to TeXML files.

    Fixed a problem with explicit compilation options being correctly parsed 
    but not processed.

    Corrected a bug regarding default init options definition for the 
    points, polygons, and bricks examples. Updated category initialization 
    in roots example.


2.8.1 - October 28, 2000

    New config file for K-Prolog 5.0.

    Improved compiler error detection and reporting of invalid directives 
    and clauses.
    
    Corrected a problem with some Prolog compilers where compiling a file 
    containing syntax errors may not close the file after the errors are 
    reported.

    Many small improvements to all documentation.
    
    Small improvements to the .xsl files and to the output of .xml files.


2.8.0 - October 1, 2000

    I have found just a few days ago that I have uploaded to the Logtalk web 
    server a development version of Logtalk 2.7.0 instead of the final one!
    To avoid confusions I decided to release a new version.

    Changed implementation of the logtalk_compile/1-2 and logtalk_load/1-2 
    predicates to only accept a list of entities instead of either an entity 
    or a list of entities, simplifying and improving the performance of these 
    predicates. Improved error reporting for the logtalk_compile/1 and 
    logtalk_load/1 predicates. Updated relevant sessions in the user and 
    reference manuals.

    Simplified the implementation of the following predicates, by sharing 
    the error checking code with the corresponding extended versions: 
    implements_protocol/2, imports_category/2, instantiates_class/2, 
    specializes_class/2, extends_protocol/2, and extends_object/2.

    Completed some missing library file dependencies documentation in some 
    examples.

    New version of the QUICK_START help file. Updated tutorial.


2.7.0 - August 24, 2000

    First release of the Logtalk standard library of objects, protocols and 
    categories.

    Rewritten all examples to use the new Logtalk standard library.

    New logtalk_load/2 and logtalk_compile/2 Logtalk built-in predicates,
    accepting a list of compiler options. See the User and Reference Manuals 
    for details.

    New XSLT file for viewing .xml files in Microsoft Internet Explorer 5.5 
    for Windows after installing the latest Microsoft XML Parser Preview 
    Release. Small improvements in all XSLT files.

    Starting with this version all config files need to provide a definition 
    for the compare/3 predicate if it is not built-in in the corresponding 
    Prolog compiler. Also, default Logtalk compiler options are now also set 
    in the config files using the lgt_default_compiler_option/2 predicate.

    Updated config file for CIAO 1.6p1. See the configs/NOTES file for 
    details.


2.6.2 - July 4, 2000

    Improved performance and error checking for the built-in predicates 
    create_object/4, create_protocol/3 and create_category/4.

    Updated config file for BinProlog 7.83.

    Many small updates to all documentation.

    New PDF versions of the documentation formated for printing (with page 
    numbers, table of contents and index)are now available in both A4 and 
    US letter formats.


2.6.1 - May 5, 2000

    Modified the structure of the automatically generated XML documenting 
    files to improve XSL translation performance. Added a new, more standard 
    compliant, XSL file to generate HTML files and renamed the old one to 
    ie5.xsl. See the xml/NOTES file for details. Corrected an error in the 
    logtalk.css CSS file.   

    Modified the definitions of predicates lgt_file_extension/2 and 
    lgt_file_name/2 in all config files.

    Updated all the user manual sessions related to automatic documentation.

    Updated all HTML documentation for future XHTML 1.0 conformance.

    Start adding documenting directives to most examples.


2.6.0 - April 27, 2000

    Added support for documentation of objects, protocols, and categories, 
    using automatic generation of XML files.

    Added info/1 and info/2 directives for documenting objects, protocols,
    categories, and predicates. Added definition of documentation file name
    extension and default file names for the DTD and XSL files to the config 
    files.

    Improved error checking for the built-in predicates create_object/4,
    create_protocol/3 and create_category/4 to also detect invalid entity 
    identifiers.

    Updated the user and reference manuals to describe the new automatic 
    documenting features.

    Updated all HTML documentation to conform to HTML 4.01 strict standard.

    Corrected some wrong cross-reference links and titles in the reference 
    and user manuals HTML pages.

    PDF versions of the manuals and tutorial are now available in both A4 
    and US letter formats.

    Corrected two errors in the searching example, one in the definition of 
    the farmer problem state space and the other when backtracking over
    performance reports.


2.5.2 - March 7, 2000

    Updated manuals to clarify some limitations of declaring and defining
    dynamic predicates inside categories and documented a way of using the 
    built-in local method this/1 to access object parameters.

    Removed references to parametric categories from the Logtalk 
    documentation (at runtime we can only access object parameters, 
    not category parameters).

    Corrected two wrong declarations of built-in methods (forall/2 and
    retractall/1) in the Logtalk pre-processor.

    Corrected bug where predicates declared in dynamic entities may have
    a "static" instead of a "dynamic" property.

    Corrected a bug in category compilation that prevented a dynamic category
    from being abolished. Speedup predicate definition lookups for categories.


2.5.1 - February 18, 2000

    Two new examples: birds, a bird identification expert system adopted 
    (with permission) from an Amzi example, and viewpoints, a set of 
    prototypes showing how to do property sharing and value sharing in 
    Logtalk.

    Renamed config file yap421.config to yap430.config to match the name of 
    the new YAP 4.3.0 public release (named 4.2.1 while on beta testing).

    Partial config file for Trinc Prolog R3.


2.5.0 - December 29, 1999

    The Logtalk pre-processor now accepts arbitrary clauses and directives
    to appear in a file before an opening entity directive. The clauses and
    directives are added unchanged to the compiled file.

    Improved performance for all kinds of message sending.

    Two new examples: reflection, showing how to implement a simple 
    class-based reflective system, and symdiff, showing how to use 
    parametric objects to implement symbolic expression differentiation 
    and simplification.

    Updated config file for the beta 8 release of SWI-Prolog 3.3.0.


2.4.0 - December 1, 1999

    Logtalk is now an Open Source project, available under Perl's Artistic 
    license.

    Two new examples: instmethods, illustrating the use of instance defined 
    methods, and classvars, showing how to implement class variables.

    Updated Logtalk grammar to explicitly allow for user-defined types
    in mode/2 directives.

    New config files for SWI-Prolog 3.3.0, SICStus Prolog 3.8 and CIAO 
    Prolog 1.4p0 (incomplete).

    Updated config file for B-Prolog 4.0.

    Updated config file for GNU Prolog to use the new call_with_args() 
    built-in predicate added in version 1.1.0.

    Updated config file for YAP Prolog to use the new call_with_args() 
    built-in predicate added in version 4.2.1.


2.3.1 - September 22, 1999

    Logtalk pre-processor updated to only report one warning per redefined
    Logtalk or Prolog built-in predicate.

    Changed some occurrences of atom "public" to "(public)" in 
    compiler/logtalk.pl file to avoid syntax errors in Prolog compilers 
    (like BinProlog) that define "public" as an operator. Also put some 
    terms between ()'s to avoid syntax errors with ALS Prolog 3.1

    Update config file for ALS Prolog to work with version 3.1.

    Updated configs/NOTES file include a workaround to use Logtalk with
    XSB 2.0, some guidelines on how to write loader utility files for
    BinProlog 7.50, and a bug in ALS Prolog 3.1 that affects Logtalk.


2.3.0 - September 12, 1999

    Metapredicate information is now stored with the other predicate 
    properties, instead of being discarded after compiling the clauses of
    a metapredicate. Added predicate property metapredicate/1. It is now 
    possible to assert clauses for dynamic metapredicates. 

    Corrected a bug in the processing of metacalls in pseudo-object user. 

    Corrected a bug in the implementation of private inheritance.
    Improved performance of protected inheritance.

    Corrected failure of processing initialization/1 and op/3 directives in 
    create_object/4, create_category/4 and create_protocol/3 built-in 
    predicates.

    Corrected a bug when calling private static category predicates from 
    importing objects. Simplified code generated for categories.

    Rewrite code for the built-in method current_predicate/1 to avoid 
    duplicated or wrong results when overriding predicate declarations 
    and to ensure that all possible argument type errors are detected.

    Changed compilation of classes that do not instantiate any (meta)class
    in order to throw the correct exception when a message is sent to them.

    Changed compilation of root objects (that do not instantiate, specialize 
    or extend other objects) so that calls to "super" (^^/1) fail (as they 
    should) instead of generating a "predicate does not exist" error message.

    Changed implementation of "super" calls (^^/1) to avoid a potential 
    endless loop problem when using these calls from the inheritance root 
    object of a reflexive class-based systems.

    Pre-processor now checks for callable and object identifier errors.
    Runtime now checks for non-instantiated messages.

    Added new example (inheritance) about public, protected and private 
    inheritance.

    Updated metapredicates, lo, kernel, and types examples. Most of the 
    code in the last two examples is being updated to form the basis of an 
    upcoming Logtalk standard library.

    Small changes in the pre-processor/runtime code for compatibility with
    ECLiPSe 4.2.2. Updated config files for this Prolog compiler.

    Rewrite some predicates in the config files for SWI-Prolog and LPA 
    Mac & WIN Prologs for improved performance.

    New tutorial session about events and monitors.

    Updated documentation to match the changes made in this version.


2.2.0 - July 10, 1999

    Implemented public, protected and private object inheritance, protocol
    implementation and category importation.
    
    New Logtalk built-in predicates instantiates_class/3, extends_object/3,
    extends_protocol/3, specializes_class/3, imports_category/3 and
    implements_protocol/3. The third argument returns the relation scope.

    Pre-processor now checks most directive errors.

    Changed ^^/1 (super call) implementation to only allow the use of a 
    single predicate call for argument and to retain the original sender
    of the message (see the updated sicstus example).

    Fixed bug that prevented directives with a variable number of arguments
    (like dynamic(), public(), uses(), ...) being recognized.

    Changed definition of predicate read_term/3 in the configs files of Amzi!,
    Aquarius, Arity, Eclipse, IC, K, LPA Mac&WIN, Master and XSB to always
    instantiates the singleton variables list to the empty list. Needed to
    prevent backtracking problems in logtalk_load/1 and logtalk_compile/1
    predicates.

    Removed choice-point in processing metacalls in predicate definitions.

    A banner with the Logtalk version is printed after loading the runtime/
    pre-processor.

    Removed variables example. The category attributes is now part of the
    kernel example. Corrected some harmless syntax errors in directives in
    kernel/attributes.lgt, kernel/monitor.lgt and miscellaneous/queens.lgt.

    Changed name of blocks example to bricks and object "block" to "brick" 
    in order to avoid problems with some Prolog compilers that use the atom 
    "block" for operators or built-in predicates.


2.1.0 - May 11, 1999

    Fixed some bugs in the definition of the pseudo-object user when sending 
    the message predicate_property/2.

    Renamed config file for Calypso to GNU Prolog.

    New config file for LPA WinProlog 4.0.

    Corrected the omission in the documentation of the Logtalk grammar of the 
    built_in entity property.

    New tutorial pages about building reflective class-based systems.

    Modified pre-processor to compile throw/1 as a control structure to 
    ensure compatibility with the GNU-Prolog compiler.

    Modified pre-processor to ensure compatibility with Prolog compilers that
    use immediate update semantics instead of the ISO logical database update.

    Improved simplification of compiled object and category clauses.

    Rewrite and clean up pre-processor code for better compiler performance.

    Several updates to the examples files.

    Changed all example loader files to wrap the call to logtalk_load/1 inside
    an initialization/1 directive for ISO standard compliance.


2.0 GM - February 9, 1999

    Removed some redundant choice-points that are being created when 
    compiling Logtalk entities.

    Small compilation speed optimizations.

    Logtalk compiled files now contain the declarations for the message 
    sending operators to ensure compatibility with some Prolog compilers.

    Changed the way Logtalk pre-processor writes directives to ensure 
    compatibility with some Prolog compilers. Corrected a bug in the
    processing of the op/3 directive.

    Updated PrologII+ config file for version 4.5.

    Changed the definitions of catch/3 and throw/1 in the config files for 
    LPA Prolog compilers.

    New config file for MasterProlog 4.1; removed config file for the 
    old BIM Prolog 4.0.

    Corrected an error in the config file for OpenProlog in the definition
    of the write_term/3 predicate.

    Added a safer definition for write_term/3 predicate in the config  
    files for Amzi, Aquarius, Arity, Eclipse, IC, K, LPA Mac, LPA Win, 
    and XSB Prolog compilers.

    Added a QUICK_START file.


2.0 Beta 3 - February 1, 1999

    Closed some encapsulation holes in the implementation of super calls.

    Changed Logtalk pre-processor to use write_term/3 instead of write/2 and 
    writeq/2 to workaround some compatibility problems with some Prolog 
    compilers.

    Changed mode operators priority and type to be compatible with the ISO
    standard.

    Modified definition of predicate read_term/3 in the config file for Amzi 
    compiler to return the atom end_of_file instead of '!EOF' at the end of
    a file (this prevented Logtalk to complete compilation any file under 
    this compiler). Improved detection of built-in predicates while compiling.

    Removed config file for wamcc. This compiler have been replaced by 
    Calypso (developed by the same author).

    Updated K-Prolog config file for version 4.50.

    Improved documentation of template config file.

    Added SCRIPT files to the kernel and types examples.

    Updated Tutorial and User and Reference Manuals.

    New end user license.


2.0 Beta 2 - November 16, 1998

    Built-ins logtalk_compile/1 and logtalk_load/1 updated to match 
    the documentation regarding thrown errors and to accept a list of
    entities to compile/load.

    Modified the examples loader utility files to make only a call to
    logtalk_load/1 by using a list of entities. This should make it easy to
    modify these files for compilers that don't support arbitrary queries
    in a file. 

    Logtalk runtime no longer tries to catch some of the errors thrown 
    by ::/2.

    Added to all config files a Logtalk predicate to check if a file 
    exists in the current working directory (used by the logtalk_load/1
    and logtalk_compile/1 Logtalk built-in predicates).

    New configs files for the K-Prolog 4.14 and Calypso 1.0b6 Prolog 
    compilers.

    Completed the config file for Open Prolog 1.03d38 (with the exception
    of lgt_current_date/3 that still have a dummy definition).

    Added a missing definition for Logtalk predicate forall/2 to the config
    file for Prolog II+ 4.4.

    Modified Logtalk pre-processor/runtime to avoid syntax errors when
    running on Open Prolog or Calypso and to remove some redundant
    choice-points that are being created when compiling categories and
    protocols.

    Modified some examples that use operators to avoid syntax errors in
    some Prolog compilers.

    Modified the implementation of the built-in method 
    predicate_property/2 to avoid duplicate answers and to throw an
    instantiation error if the first argument is not bound.

    Modified definition of the pseudo-object user to hide Logtalk pre-
    processor predicates from the current_predicate/1 built-in method and
    to ensure that the predicate_property/2 built-in method returns
    Logtalk defined predicate properties for built-in Logtalk and Prolog
    predicates.

    Modified Prolog code generated by the pre-processor to further minimize
    possible conflicts with user defined predicates.

    Added a lgt_predicate_property/2 predicate to the config files to
    improve Logtalk portability.

    Updated Tutorial and User and Reference Manuals.


2.0 Beta 1 - October 18, 1998

    Added basic support for implementation multi-inheritance.

    Logtalk pre-processor updated to try to detect misspelt local 
    predicate calls.

    First public beta.


2.0 Alpha 1 - July, 1998

    First release for registered users.