12 Bugs
There is a slight difference in syntax between ML-Lex and ML-Yacc.
In ML-Lex, semantic actions must be followed by a semicolon but
in ML-Yacc semantic actions cannot be followed by a semicolon.
The syntax should be the same. ML-Lex also produces structures with
two different signatures, but it should produce structures with just
one signature. This would simplify some things.