From: Markus Triska <triska@metalevel.at>
Date: Sun, 21 Aug 2022 11:51:12 +0000 (+0200)
Subject: ENHANCED: Use '$skip_max_list'/4 for greater efficiency of nth0/3.
X-Git-Tag: v0.9.1^2~31
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=7c5318b784c863d218cd9866f5155a288dcc404d;p=scryer-prolog.git

ENHANCED: Use '$skip_max_list'/4 for greater efficiency of nth0/3.

This is now possible due to 4c7e2eb8614da9c04f2286f6116b468017fb442c.

See #1529 for the suggestion by @UWN.
---

diff --git a/src/lib/lists.pl b/src/lib/lists.pl
index 52f862bb..7cfffa17 100644
--- a/src/lib/lists.pl
+++ b/src/lib/lists.pl
@@ -247,16 +247,10 @@ nth0(N, Es, E) :-
         can_be(integer, N),
         can_be(list, Es),
         (   integer(N) ->
-            nth0_index(N, Es, E)
+            '$skip_max_list'(N, N, Es, [E|_])
         ;   nth0_search(N, Es, E)
         ).
 
-nth0_index(0, [E|_], E) :- !.
-nth0_index(N, [_|Es], E) :-
-        N > 0,
-        N1 is N - 1,
-        nth0_index(N1, Es, E).
-
 nth0_search(N, Es, E) :-
         nth0_search(0, N, Es, E).