Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!jarthur!uci-ics!rfg
From: rfg@ics.uci.edu (Ronald Guilmette)
Newsgroups: comp.lang.c++
Subject: Re: zortech problem with lex
Message-ID: <26073795.10139@paris.ics.uci.edu>
Date: 21 Mar 90 08:13:09 GMT
References: <6300008@ux1.cso.uiuc.edu> <24800002@sunb6> <25ECE752.29589@paris.ics.uci.edu> <10541@alice.UUCP> <6553@cadillac.CAD.MCC.COM> <25F8C92A.9349@paris.ics.uci.edu> <3742@tukki.jyu.fi>
Reply-To: rfg@ics.uci.edu (Ronald Guilmette)
Organization: UC Irvine Department of ICS
Lines: 43

In article <3742@tukki.jyu.fi> sakkinen@jytko.jyu.fi (Markku Sakkinen) writes:
>In article <25F8C92A.9349@paris.ics.uci.edu> rfg@ics.uci.edu (Ronald Guilmette) writes:
>>In article <6553@cadillac.CAD.MCC.COM> ned@MCC.COM (Ned Nowotny) writes:
>>>
>>>Given the imprecise nature of the C++ specification, I am more than a
>>>little disappointed that the language does not have a grammar expressible
>>>in BNF form that will accept all legal strings and reject all illegal
>>>strings.
>>
>>As Joe English also points out, this is utter nonsense. [...]
>>>... While it may be
>>>true that some LALR(1) grammar will accept all legal C++ strings, the fact
>>>that the grammar must also accept illegal strings makes the claim that
>>>C++ is somehow a LALR(1) language something less than useful.
>>
>>I agree that in practice, nobody actually is stupid enough to use V* as their
>>LALR(1) grammar for parsing C++ or other languages, but just because the
>>statement "C++ is LALR(1)" may not be "useful" does not mean that it is
>>not 100% accurate.  In fact, I believe that it is.
>
>Sorry, Mr. Guilmette, I think it is _you_ who are repeating the same
>utter nonsense too many times in this group. Please stand back for
>a while and reflect on how vacuous any grammatical classification
>of languages becomes is one takes your attitude. Alternatively,
>go post your opinion to the comp.theory group (or comp.compilers)
>and get your knuckles rapped on by real experts.

I believe that I failed to make my point clearly enough.  I used the
(admitedly extreme) example of V* as a grammar for C++ just to make
it quite evident that a C++ grammar could be LALR(1).

I only did this for the sake of argument.  As should be demonstrated
by Jim Roskind's grammar, you need not devolve the grammar all the
way down to V* to get it to be LALR(1).  Quite the contrary.
If you are willing to do just a few more things with semantic analysis
rather than syntax analysis (relative to what current C++ implementors
seem to be doing) then you can in fact have a useful and practical LALR(1)
grammar for C++.  That was my point.  I just stated it badly.


// Ron Guilmette (rfg@ics.uci.edu)
// C++ Entomologist
// Motto:  If it sticks, force it.  If it breaks, it needed replacing anyway.