Include Paulo Moura's Logtalk OO LP system

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@53 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

Logtalk/library/integer.lgt

@@ -0,0 +1,46 @@
+
+:- object(integer,
+	extends(number)).
+
+
+	:- info([
+		version is 1.0,
+		authors is 'Paulo Moura',
+		date is 2000/7/24,
+		comment is 'Integer data type predicates.']).
+
+
+	:- public(between/3).
+
+	:- mode(between(+integer, +integer, ?integer), zero_or_more).
+
+	:- info(between/3, [
+		comment is 'Returns integers in the interval defined by the two first arguments.',
+		argnames is ['Lower', 'Upper', 'Integer']]).
+
+
+	between(Lower, Upper, Integer) :-
+		integer(Lower),
+		integer(Upper),
+		(var(Integer) ->
+			Lower =< Upper,
+			generate(Lower, Upper, Integer)
+			;
+			integer(Integer),
+			Lower =< Integer,
+			Integer =< Upper).
+
+
+	generate(Lower, _, Lower).
+
+	generate(Lower, Upper, Integer) :-
+		Lower < Upper,
+		Next is Lower + 1,
+		generate(Next, Upper, Integer).
+
+
+	valid(Integer) :-
+		integer(Integer).
+
+
+:- end_object.