From: Mark Thom <markjordanthom@gmail.com>
Date: Sun, 3 Mar 2019 09:50:49 +0000 (-0700)
Subject: improve reverse/2
X-Git-Tag: v0.8.110~217
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=74521a93d3e0e7e39a6bd6fa82932709746e3e3a;p=scryer-prolog.git

improve reverse/2
---

diff --git a/src/prolog/lib/lists.pl b/src/prolog/lib/lists.pl
index 078b9674..e96d677d 100644
--- a/src/prolog/lib/lists.pl
+++ b/src/prolog/lib/lists.pl
@@ -41,11 +41,11 @@ append([X|L], R, [X|S]) :- append(L, R, S).
 
 memberchk(X, Xs) :- member(X, Xs), !.
 
-reverse(Xs, Ys) :- reverse(Xs, [], Ys).
+reverse(Xs, Ys) :- reverse(Xs, Ys, [], [], Xs).
 
-reverse([], Ys, Ys).
-reverse([H|T], Ps, Rs) :-
-    reverse(T, [H|Ps], Rs).
+reverse([], [], XsRev, YsRev, YsRev).
+reverse([X1|Xs], [Y1|Ys], XsPreludeRev, YsPreludeRev, Xss) :-
+    reverse(Xs, Ys, [X1|XsPreludeRev], [Y1|YsPreludeRev], Xss).
 
 maplist(_, []).
 maplist(Cont1, [E1|E1s]) :-
@@ -86,4 +86,3 @@ maplist(_, [], [], [], [], [], [], [], []).
 maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s], [E5|E5s], [E6|E6s], [E7|E7s], [E8|E8s]) :-
     call(Cont, E1, E2, E3, E4, E5, E6, E7),
     maplist(Cont, E1s, E2s, E3s, E4s, E5s, E6s, E7s, E8s).
-