Hi all, The production [U] "boolean-expression" is the same production as [42] "forall-clause". The "forall-clause" is reachable through production [39] "boolean-primitive" which is reachable through "boolean-expression". Suggestion: Remove [U] and add "==> not some ..." to [42]. Best regards, Lars -- Semagia <http://www.semagia.com/>