From a86019d53ba8c5534cc883e0c1cec89499abb1fd Mon Sep 17 00:00:00 2001
From: notoria <notoria@users.noreply.github.com>
Date: Wed, 13 May 2020 21:19:47 +0200
Subject: [PATCH] Enhanced between/3

---
 src/prolog/lib/between.pl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/prolog/lib/between.pl b/src/prolog/lib/between.pl
index 16c73145..4ce92db7 100644
--- a/src/prolog/lib/between.pl
+++ b/src/prolog/lib/between.pl
@@ -9,7 +9,11 @@ between(Lower, Upper, X) :-
     must_be(integer, Lower),
     must_be(integer, Upper),
     can_be(integer, X),
-    between_(Lower, Upper, X).
+    (   nonvar(X) ->
+        Lower =< X,
+        X =< Upper
+    ;   between_(Lower, Upper, X)
+    ).
 
 between_(Lower, Upper, Lower) :-
     Lower =< Upper.
-- 
2.54.0