root/tags/lgt2171/RELEASE_NOTES

=================================================================
Logtalk - Object oriented extension to Prolog
Release 2.17.1

Copyright (c) 1998-2004 Paulo Moura.  All Rights Reserved.
=================================================================


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


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 categoty, 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 depracated 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 - Sptember 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 togles 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 stylesheets 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 
    suporious 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.

    Rewrited 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 ocorrences 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 "Missionaires 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, ilustrating 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 warmless 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 definiton
    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 arbritrary 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.