Re: Useless nonterminals - what and why?

[Akim Demaille]

>>>>> "Matthew" == Matthew Palmer <address@hidden> writes:

Matthew> OK, hacking on somebody else's bison file, and I have gotten
Matthew> this message. Not real sure exactly what it means, beyond a
Matthew> definition somebody gave that "A useless nonterminal is one
Matthew> which doesn't produce any strings" or similar.

That's a pretty theoretical definition, which in essence means this
symbol is not reachable starting from the start symbol.  Typically,
it's not used in any rule.

But Bison is usually quite good at error message: what exactly did it
say?  Your snippet has several flaws, but most probably due to the
fact that you cut some other relevant parts.  In particular I can't
see any useless nonterminal here.