update between/3 to allow inf as upper bound

2020-02-19 15:55:56 -07:00
parent d3da2683cb
commit 617f803355
1 changed files with 9 additions and 4 deletions
--- a/src/prolog/lib/between.pl
+++ b/src/prolog/lib/between.pl
@@ -6,10 +6,15 @@
 :- use_module(library(error)).

 between(Lower, Upper, X) :-
-    must_be(integer, Lower),
-    must_be(integer, Upper),
-    can_be(integer, X),
-    between_(Lower, Upper, X).
+    (  Upper == inf ->
+       must_be(integer, Lower),
+       can_be(integer, X),
+       enumerate_nats(Lower, X)
+    ;  must_be(integer, Lower),
+       must_be(integer, Upper),
+       can_be(integer, X),
+       between_(Lower, Upper, X)
+    ).

 between_(Lower, Upper, Lower) :-
    Lower =< Upper.