Bugfix: Incorrect detection of unknown PRISM language functions.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@191 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/parser/ExpressionFunc.java

@@ -60,7 +60,7 @@ public class ExpressionFunc extends ExpressionNary
 		name = s;
 		// determine and set code
 		n = names.length;
-		code = 0;
+		code = -1;
 		for (i = 0; i < n; i++) {
 			if (s.equals(names[i])) {
 				code = i;