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From: jbuck@galileo.berkeley.edu (Joe Buck)
Newsgroups: comp.lang.c++
Subject: Re: C++ Grammar
Message-ID: <11373@pasteur.Berkeley.EDU>
Date: 23 Feb 91 02:28:16 GMT
References: <3786@lupine.NCD.COM> <1991Feb08.130548.6878@iti.com> <70609@microsoft.UUCP> <112@shasta.Stanford.EDU>
Sender: news@pasteur.Berkeley.EDU
Reply-To: jbuck@galileo.berkeley.edu (Joe Buck)
Lines: 24

In article <112@shasta.Stanford.EDU>, shap@shasta.Stanford.EDU (shap) writes:
|> The problem with Roskind's grammar (at least the last time I looked - it
|> may have been updated in the past few months) is that it requires the
|> lexer to resolve "typedef" v/s "identifier", which is probably the most
|> difficult problem in the language as far as parsing goes.  If anyone has
|> built a tool that overcomes this limitation, including the associated
|> symtab support, I would be interested to see it.

I've seen this point raised for years and years and years, and I've never
understood it (mainly about typedefs in C, but it applies to C++).  Why
do people object so strenously to the parser asking the lexer for help
when distinguishing identifiers from types?  The implementation is obvious,
it's clean, it's easy to do.  Once a token has been declared as a type,
mark it as such in the symbol table, so the next time the token appears,
the lexer returns the token indicating that it's a type, not an identifier.
It's simple, it's clean, and it works.  But yet there is a faction that
screams about the "impurity" of it.  Why?

Actually, I doubt if C++ can be parsed without using this trick, with
anyone's grammar.

--
Joe Buck
jbuck@galileo.berkeley.edu	 {uunet,ucbvax}!galileo.berkeley.edu!jbuck