From abca5fc4058aa1f98109525b779670d5d34ed567 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Tue, 23 Aug 2022 21:21:17 +0200
Subject: [PATCH] better implementation of list_si/1

Per discussion in https://github.com/mthom/scryer-prolog/pull/1589.
---
 src/lib/si.pl | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/lib/si.pl b/src/lib/si.pl
index 7fc3a596..d697c8a8 100644
--- a/src/lib/si.pl
+++ b/src/lib/si.pl
@@ -43,9 +43,15 @@ integer_si(I) :-
 atomic_si(AC) :-
    functor(AC,_,0).
 
-list_si(L) :-
-   \+ \+ length(L, _),
-   sort(L, _).
+% list_si(L) :-
+%    \+ \+ length(L, _),
+%    sort(L, _).
+
+list_si(L0) :-
+   '$skip_max_list'(_,_, L0,L),
+   (  nonvar(L) -> L = []
+   ;  throw(error(instantiation_error, list_si/1))
+   ).
 
 chars_si(Cs) :-
    list_si(Cs),
-- 
2.54.0