add meta_predicate declaration for must_succeed/1

diff --git a/src/lib/clpz.pl b/src/lib/clpz.pl
index e72a33c145313152517be5daa4f7d6e9445a1403..b7fa0ea7f34a3ac750318028b98e18ffd24946fd 100644 (file)
--- a/src/lib/clpz.pl
+++ b/src/lib/clpz.pl
@@ -5884,10 +5884,12 @@ difference_arcs([V|Vs], FL0) -->
 
 writeln(T) :- write(T), nl.
 
+:- meta_predicate must_succeed(0).
+
 must_succeed(G) :-
-    (G -> true
-     ;write(failed-G), halt
-    ).
+        (   G -> true
+        ;   throw(failed-G)
+        ).
 
 enumerate([], _) --> [].
 enumerate([N|Ns], V) -->