[Mono-dev] Mono-devel-list Digest, Vol 72, Issue 10

[Chris Seaton]

Just be aware that not all grammars can express all languages, and so not all parser-generators can parse all languages. GNU Make does not use a parser-generator to parse Makefiles - perhaps there's a good reason. You say that a lexer for Make would be very context-dependent, and most parse-generators don't handle that well at all.

Generally, parsing is a pretty simple problem in the first place and I think that parser-generators often introduce more problems than they solve. Why can't you nest block comments in C? Because of a limited lexer-generator.

Do a quick google for a Make grammar for Antlr or Jay and see if anyone else has managed it.

Regards,

Chris Seaton

On 7 Apr 2011, at 19:30, Tom Spink wrote:

> On 7 April 2011 05:56, Sharp BladeÎÞºñÖ®ÈÐ <sharper.than.bladez at gmail.com> wrote:
>> Hello!
>> 
>> Well,since I have a lot of experience with Antlr on C#,it does not
>> seem to be a good choice to use jay.And the makefile grammar is quiet
>> simple,I wonder if I could write the parser by hand.
>> 
>> Sharp
> 
> Hello!
> 
> Unfortunately, the Makefile grammar is not as simple as you think, and
> simple or not, writing parsers by hand is generally discouraged
> nowadays, for the simple reason of:- why re-invent the wheel?
> 
> There are tools available for parser (and lexer) generation, which are
> tried and tested and I think you'll find you'll make more mistakes
> rolling your own parser, than you'll get if you use a parser
> generator.
> 
> Also, writing an LALR, LR(1) or indeed any bottom-up parser by hand is
> quite challenging - even for the simplest grammars.  If you really
> went down this route, you'd be best off writing a top-down parser,
> which can exponentially increase in size as a grammar increases.  But,
> I still wouldn't recommend it, as the more you get into the grammar,
> the more you'll find yourself changing your parser and wishing you'd
> used a generator.
> 
> You'll also need to construct a lexer for the Makefile - which is
> itself a daunting challenge.  Particularly because the Makefile syntax
> is really quite complex (since it's heavily context-based), so you'd
> have trouble implementing a lexer and parser yourself.
> 
> Hope this helps,
> 
> -- Tom.
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