diff -r fb6192488b91 -r 3d04ee04966d progs/fun_tokens.scala
--- a/progs/fun_tokens.scala	Sun Oct 13 00:53:20 2019 +0100
+++ b/progs/fun_tokens.scala	Mon Oct 14 00:02:24 2019 +0100
@@ -249,8 +249,11 @@
 }
 
 
-def tokenise(s: String) : List[Token] = 
-  lexing_simp(FUN_REGS, s).collect(token)
+def tokenise(s: String) : List[Token] = {
+  val tks = lexing_simp(FUN_REGS, s).collect(token)
+  if (tks.length != 0) tks
+  else { println (s"Tokenise Error") ; sys.exit(-1) }     
+}
 
 def serialise[T](fname: String, data: T) = {
   import scala.util.Using
@@ -267,4 +270,4 @@
 }
 
 
-}
\ No newline at end of file
+}