From 2566ebcee520d377e6c30ab7e11fd3a0ad13f8cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa=20II?= <vsc@dcc.fc.up.pt>
Date: Tue, 20 Apr 2010 23:49:14 +0100
Subject: [PATCH] make predsort a system predicate.

---
 docs/yap.tex            | 10 ++++++++
 library/dialect/swi.yap | 56 -----------------------------------------
 pl/sort.yap             | 43 +++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 56 deletions(-)

diff --git a/docs/yap.tex b/docs/yap.tex
index a2c43eaf6..42346f5ff 100644
--- a/docs/yap.tex
+++ b/docs/yap.tex
@@ -3743,6 +3743,16 @@ would return:
 S = [1-b,1-a,1-b,2-c,3-a]
 @end example
 
+@item predsort(+@var{Pred}, +@var{List}, -@var{Sorted})
+@findex predsort/3
+@snindex predsort/3
+@cnindex predsort/3
+Sorts similar to sort/2, but determines the order of two terms by
+calling @var{Pred}(-@var{Delta}, +@var{E1}, +@var{E2}) . This call must
+unify @var{Delta} with one of @code{<}, @code{>} or @code{=}. If
+built-in predicate compare/3 is used, the result is the same as
+sort/2.
+
 @item length(?@var{L},?@var{S})
 @findex length/2
 @syindex length/2
diff --git a/library/dialect/swi.yap b/library/dialect/swi.yap
index dad6fdafd..7dc069c18 100755
--- a/library/dialect/swi.yap
+++ b/library/dialect/swi.yap
@@ -137,62 +137,6 @@ user:file_search_path(foreign, swi(ArchLib)) :-
         atom_concat('lib/', Arch, ArchLib).
 user:file_search_path(foreign, swi(lib)).
 
-:- meta_predicate prolog:predsort(:,+,-).
-
-prolog:plus(X, Y, Z) :-
-       integer(X),
-       integer(Y), !,
-       Z is X + Y.
-prolog:plus(X, Y, Z) :-
-       integer(X),
-       integer(Z), !,
-       Y is Z - X.
-prolog:plus(X, Y, Z) :-
-       integer(Y),
-       integer(Z), !,
-       X is Z - Y.
-
-%%	predsort(:Compare, +List, -Sorted) is det.
-%
-%	 Sorts similar to sort/2, but determines  the order of two terms
-%	 by calling Compare(-Delta, +E1,  +E2).   This  call  must unify
-%	 Delta with one of <, > or =. If built-in predicate compare/3 is
-%	 used, the result is the same as sort/2. See also keysort/2.
-
-prolog:predsort(P, L, R) :-
-	length(L, N), 
-	predsort(P, N, L, _, R1), !, 
-	R = R1.
-
-predsort(P, 2, [X1, X2|L], L, R) :- !, 
-	call(P, Delta, X1, X2),
-	sort2(Delta, X1, X2, R).
-predsort(_, 1, [X|L], L, [X]) :- !.
-predsort(_, 0, L, L, []) :- !.
-predsort(P, N, L1, L3, R) :-
-	N1 is N // 2, 
-	plus(N1, N2, N), 
-	predsort(P, N1, L1, L2, R1), 
-	predsort(P, N2, L2, L3, R2), 
-	predmerge(P, R1, R2, R).
-
-sort2(<, X1, X2, [X1, X2]).
-sort2(=, X1, _,  [X1]).
-sort2(>, X1, X2, [X2, X1]).
-
-predmerge(_, [], R, R) :- !.
-predmerge(_, R, [], R) :- !.
-predmerge(P, [H1|T1], [H2|T2], Result) :-
-	call(P, Delta, H1, H2),
-	predmerge(Delta, P, H1, H2, T1, T2, Result).
-
-predmerge(>, P, H1, H2, T1, T2, [H2|R]) :-
-	predmerge(P, [H1|T1], T2, R).
-predmerge(=, P, H1, _, T1, T2, [H1|R]) :-
-	predmerge(P, T1, T2, R).
-predmerge(<, P, H1, H2, T1, T2, [H1|R]) :-
-	predmerge(P, T1, [H2|T2], R).
-
 
 %
 % maybe a good idea to eventually support this in YAP.
diff --git a/pl/sort.yap b/pl/sort.yap
index 91eee683e..d6c2620eb 100644
--- a/pl/sort.yap
+++ b/pl/sort.yap
@@ -53,3 +53,46 @@ msort(L,O) :-
 keysort(L,O) :-
 	'$keysort'(L,O).
 
+:- meta_predicate prolog:predsort(:,+,-).
+
+%%	predsort(:Compare, +List, -Sorted) is det.
+%
+%	 Sorts similar to sort/2, but determines  the order of two terms
+%	 by calling Compare(-Delta, +E1,  +E2).   This  call  must unify
+%	 Delta with one of <, > or =. If built-in predicate compare/3 is
+%	 used, the result is the same as sort/2. See also keysort/2.
+
+predsort(P, L, R) :-
+	length(L, N), 
+	predsort(P, N, L, _, R1), !, 
+	R = R1.
+
+predsort(P, 2, [X1, X2|L], L, R) :- !, 
+	call(P, Delta, X1, X2),
+	sort2(Delta, X1, X2, R).
+predsort(_, 1, [X|L], L, [X]) :- !.
+predsort(_, 0, L, L, []) :- !.
+predsort(P, N, L1, L3, R) :-
+	N1 is N // 2, 
+	plus(N1, N2, N), 
+	predsort(P, N1, L1, L2, R1), 
+	predsort(P, N2, L2, L3, R2), 
+	predmerge(P, R1, R2, R).
+
+sort2(<, X1, X2, [X1, X2]).
+sort2(=, X1, _,  [X1]).
+sort2(>, X1, X2, [X2, X1]).
+
+predmerge(_, [], R, R) :- !.
+predmerge(_, R, [], R) :- !.
+predmerge(P, [H1|T1], [H2|T2], Result) :-
+	call(P, Delta, H1, H2),
+	predmerge(Delta, P, H1, H2, T1, T2, Result).
+
+predmerge(>, P, H1, H2, T1, T2, [H2|R]) :-
+	predmerge(P, [H1|T1], T2, R).
+predmerge(=, P, H1, _, T1, T2, [H1|R]) :-
+	predmerge(P, T1, T2, R).
+predmerge(<, P, H1, H2, T1, T2, [H1|R]) :-
+	predmerge(P, T1, [H2|T2], R).
+