From: Markus Triska <triska@metalevel.at>
Date: Mon, 7 Mar 2022 22:38:30 +0000 (+0100)
Subject: ENHANCED: call_nth(Goal, 0) now fails, correct error for N < 0.
X-Git-Tag: v0.9.1~124^2
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=69e52d1ed80d9bdc33ea1d646f816953e1ac3cdf;p=scryer-prolog.git

ENHANCED: call_nth(Goal, 0) now fails, correct error for N < 0.

This addresses #1307.
---

diff --git a/src/lib/iso_ext.pl b/src/lib/iso_ext.pl
index e614b1f6..6a1f007a 100644
--- a/src/lib/iso_ext.pl
+++ b/src/lib/iso_ext.pl
@@ -203,8 +203,11 @@ partial_string_tail(String, Tail) :-
 
 call_nth(Goal, N) :-
     can_be(integer, N),
-    (   integer(N), N =< 0,
-        domain_error(positive_integer, N, call_nth/2)
+    (   integer(N) ->
+        (   N < 0 ->
+            domain_error(not_less_than_zero, N, call_nth/2)
+        ;   N > 0
+        )
     ;   true
     ),
     setup_call_cleanup(call_nth_nesting(ID),