Returns for all grammar rules:
- the recursion type (no recursion, direct or indirect recursion). - the left-recursion type (no left-recursion, direct left-recursion, hidden, or indirect) - the null-match for a grammar's rules: whether the rule can succeed while consuming nothing. - the possibility of an infinite loop (if 'e' can null-match, then 'e*' can enter an infinite loop).
This kind of potential problem can be detected statically and should be transmitted to the grammar designer.