root/trunk/examples/metapredicates/SCRIPT.txt

================================================================
Logtalk - Open source object-oriented logic programming language
Release 2.35.0

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.
================================================================


% start by loading the example and the required library files:

| ?- logtalk_load(metapredicates(loader)).
...


% note that "user" is a pseudo-object representing the Prolog database;
% therefore, the integer comparisons are performed using the standard
% Prolog built-in predicates

| ?- sort(user)::sort([3, 1, 4, 2, 9], Sorted).

call: partition([1,4,2,9],3,_358,_359)
exit: partition([1,4,2,9],3,[1,2],[4,9])
call: sort([1,2],_740)
call: partition([2],1,_967,_968)
exit: partition([2],1,[],[2])
call: sort([],_1300)
exit: sort([],[])
call: sort([2],_1539)
call: partition([],2,_1765,_1766)
exit: partition([],2,[],[])
call: sort([],_2093)
exit: sort([],[])
call: sort([],_2332)
exit: sort([],[])
exit: sort([2],[2])
exit: sort([1,2],[1,2])
call: sort([4,9],_2831)
call: partition([9],4,_3058,_3059)
exit: partition([9],4,[],[9])
call: sort([],_3391)
exit: sort([],[])
call: sort([9],_3630)
call: partition([],9,_3856,_3857)
exit: partition([],9,[],[])
call: sort([],_4184)
exit: sort([],[])
call: sort([],_4423)
exit: sort([],[])
exit: sort([9],[9])
exit: sort([4,9],[4,9])

Sorted = [1,2,3,4,9]
yes


% call the meta-predicate apply/2 directly:

| ?- metapreds::test_this.

1, metapreds
yes


% send an apply/2 message to self:

| ?- descendant::test_self.

2, descendant
yes


% send an apply/2 message from another object:

| ?- test::test_obj.

3, test
yes


% use the partition/4 predicate with a predicate defined in the
% pseudo-object "user":

| ?- meta::partition(even_integer, [1,2,3,4,5], Included, Excluded).

Included = [2, 4]
Excluded = [1, 3, 5]
yes


% use the fold_left/4 predicate with a predicate defined in the
% pseudo-object "user":

| ?- meta::fold_left(sum_squares, 0, [1,2,3], Result).

Result = 34
yes


% use the fold_left/4 and fold_right/4 predicates with the atom_concat/3
% Prolog built-in predicate:

| ?- meta::fold_left(atom_concat, 'PREFIX', [abc,def,ghi], Result).

Result = 'PREFIXabcdefghi'
yes

| ?- meta::fold_right(atom_concat, 'SUFIX', [abc,def,ghi], Result).

Result = abcdefghiSUFIX
yes


% use the fold_left/4 predicate with predicates defined in the object
% "predicates":

| ?- meta::fold_left(predicates::sum, 0, [1,2,3,4,5], Result).

Result = 15
yes

| ?- meta::fold_left(predicates::product, 1, [1,2,3,4,5], Result).

Result = 120
yes

| ?- meta::fold_left(predicates::tuple, (0,0), [(1,2), (3,4), (6,4)], Result).

Result = (10, 10)
yes


% use the map/2-3 predicates with some Prolog built-in predicates:

| ?- meta::map(integer, [1,2,3,4,5]).

yes

| ?- meta::map(char_code, [a,b,c,d,e], Codes).

Codes = [97, 98, 99, 100, 101]
yes