Anyone have comments on ydb (yacc debugger)?

[Don Libes]

I'm looking at an advertisement for ydb, a yacc replacement with
symbolic debugger (compatible with yacc) from Bloomsbury Software
Group.

It does a number of nice things such as showing symbols (either
terminals or non-terminals) which can follow another symbol,
explaining conflicts in much better ways, or allow you to browse
through the value stack.

Before I plunk down $1000, I was wondering if anyone had experience
with it since I've never heard of it before.  It really sounds like a
dream come true.

Is there anything else like this?

Don Libes          libes at cme.nist.gov      ...!uunet!cme-durer!libes