Logtalk 2.29.1 files.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1744 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

Logtalk/examples/metapredicates/NOTES.txt

@@ -1,6 +1,6 @@
 =================================================================
 Logtalk - Object oriented extension to Prolog
-Release 2.28.2
+Release 2.29.1
 
 Copyright (c) 1998-2006 Paulo Moura.  All Rights Reserved.
 =================================================================

Logtalk/examples/metapredicates/SCRIPT.txt

@@ -1,6 +1,6 @@
 =================================================================
 Logtalk - Object oriented extension to Prolog
-Release 2.28.2
+Release 2.29.1
 
 Copyright (c) 1998-2006 Paulo Moura.  All Rights Reserved.
 =================================================================
@@ -59,3 +59,30 @@ exit: sort([4,9],[4,9])
 Sorted = [1,2,3,4,9] ? 
 
 yes
+
+
+% call the meta-predicate apply/2 directly:
+
+| ?- meta::test_this.
+
+1, meta
+
+yes
+
+
+% send an apply/2 message to self:
+
+| ?- desc::test_self.
+
+2, desc
+
+yes
+
+
+% send an apply/2 message from another object:
+
+| ?- test::test_obj.
+
+3, test
+
+yes

Logtalk/examples/metapredicates/closures.lgt

@@ -0,0 +1,56 @@
+
+/*	Logtalk meta-predicates accept not only goals but also closures
+	as meta-arguments as illustrated in this example
+*/
+
+
+:- object(meta).
+
+	% the meta_predicate/1 directive below changes the interpretation of meta-calls on apply/2
+	% clauses; the integer argument ("1") implies that the first argument is a closure that will 
+	% be used to construct a goal by appending exactly one additional argument
+
+	:- public(apply/2).
+	:- mode(apply(+callable, ?term), zero_or_more).
+	:- meta_predicate(apply(1, *)).
+
+	apply(Closure, Arg) :-		% the Logtalk compiler verifies that any closure which is a
+		call(Closure, Arg).		% meta-argument is used within a call/N method that honors the
+								% meta-predicate directive (in this case, apply(1, *) => call/2)
+
+	:- public(test_this/0).		% simple predicate for testing calls to a local meta-predicate
+
+	test_this :-
+		apply(foo(X), Y),
+		write((X, Y)), nl.
+
+	foo(1, meta).
+
+:- end_object.
+
+
+:- object(desc,
+	extends(meta)).	
+
+	:- public(test_self/0).		% simple predicate for testing calls to a meta-predicate
+								% defined in an ancestor object
+	test_self :-
+		::apply(foo(X), Y),
+		write((X, Y)), nl.
+
+	foo(2, desc).
+
+:- end_object.
+
+
+:- object(test).
+
+	:- public(test_obj/0).		% simple predicate for testing calls to a meta-predicate
+								% defined in another object
+	test_obj :-
+		meta::apply(foo(X), Y),
+		write((X, Y)), nl.
+
+	foo(3, test).
+
+:- end_object.

Logtalk/examples/metapredicates/loader.lgt

@@ -1,13 +1,15 @@
 
 :- initialization(
-	logtalk_load(
-		[metapredicates])). 
+	logtalk_load([
+		closures,
+		metapredicates])). 
 
 /*
 If you intend to use the FOP XSL:FO processor for generating PDF documenting
 files, comment the directive above and uncomment the directive below
 
 :- initialization(
-	logtalk_load(
-		[metapredicates], [xmlsref(standalone)])).
+	logtalk_load([
+		closures,
+		metapredicates], [xmlsref(standalone)])).
 */