From 69e52d1ed80d9bdc33ea1d646f816953e1ac3cdf Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Mon, 7 Mar 2022 23:38:30 +0100
Subject: [PATCH] ENHANCED: call_nth(Goal, 0) now fails, correct error for N <
 0.

This addresses #1307.
---
 src/lib/iso_ext.pl | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

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),
-- 
2.54.0