Fw:

Fw:

[Erik de Castro Lopo]

Begin forwarded message:

Date: 24 Aug 2004 19:21:21 +1000
From: skaller <skaller@users.sourceforge.net>
To: SooHyoung Oh <shoh@compiler.kaist.ac.kr>
Cc: caml-list <caml-list@pauillac.inria.fr>
Subject: Re: [Caml-list] (Release) ocamllex tutorial (ver 0.1)


On Tue, 2004-08-24 at 18:07, SooHyoung Oh wrote:

> Any comment will be appreciated.

It looks very good!

> This tutorial is work-in-progress. The latest version can be found at
> http://pllab.kaist.ac.kr/~shoh/ocaml/ocamllex_ocamlyacc/ocamllex-tutorial/index.html.

First -- you haven't explained how to use the new argument
feature. A good example would be to take the non-reentrant
line counting example and show how to make it re-entrant
by passing an object containing the counters.

To justify not using a global variable, you can extend
the example to allow for recursively counting #include
files (or something similar :)

The second thing I'd like to see here is an example
showing the common technique of lexing an identifier
and then using a lookup table to see if it is keyword:
this is done because (a) it is possible and (b) it
simplifies the lexer which otherwise needs a huge
number of states.

The third thing I'd like to see is a more functional example
where the lexer isn't just executing code for side effects.
All your examples have the lexer tail calling itself: but
most real lexing applications do not do this, instead
you call the lexer repeatedly from a driver loop.

In particular Ocamlyacc calls Ocamllex to lex one
token at a time.

Finally -- since your tutorial is Ocaml specific,
I'd like to see some information on lexbufs.
Are they functional? Can I write a backtracking
functional parser that just 'goes backwards'
in the input stream using a lexbuf to allow
re-lexing some input? 

How do i cope with the fact
that lexbufs think they're reading named
files with lines in them .. what if this isn't so?

This is actually a design fault which is unfortunately
propagated to Ocamlyacc.

-- 
John Skaller, mailto:skaller@users.sf.net
voice: 061-2-9660-0850, 
snail: PO BOX 401 Glebe NSW 2037 Australia
Checkout the Felix programming language http://felix.sf.net



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Begin forwarded message:

Date: Tue, 24 Aug 2004 16:56:17 +0200
From: Nicolas Rougnon-Glasson <nicolas.rougnon-glasson@libertysurf.fr>
To: caml-list <caml-list@pauillac.inria.fr>
Subject: Re: [Caml-list] (Release) ocamllex tutorial (ver 0.1)


another interesting example is the use of several lexer functions (like 
in the ocaml lexer itself...), to analyse properly string literals and 
nested comments.

skaller wrote:

>On Tue, 2004-08-24 at 18:07, SooHyoung Oh wrote:
>
>  
>
>>Any comment will be appreciated.
>>    
>>
>
>It looks very good!
>
>  
>
>>This tutorial is work-in-progress. The latest version can be found at
>>http://pllab.kaist.ac.kr/~shoh/ocaml/ocamllex_ocamlyacc/ocamllex-tutorial/index.html.
>>    
>>
>
>First -- you haven't explained how to use the new argument
>feature. A good example would be to take the non-reentrant
>line counting example and show how to make it re-entrant
>by passing an object containing the counters.
>
>To justify not using a global variable, you can extend
>the example to allow for recursively counting #include
>files (or something similar :)
>
>The second thing I'd like to see here is an example
>showing the common technique of lexing an identifier
>and then using a lookup table to see if it is keyword:
>this is done because (a) it is possible and (b) it
>simplifies the lexer which otherwise needs a huge
>number of states.
>
>The third thing I'd like to see is a more functional example
>where the lexer isn't just executing code for side effects.
>All your examples have the lexer tail calling itself: but
>most real lexing applications do not do this, instead
>you call the lexer repeatedly from a driver loop.
>
>In particular Ocamlyacc calls Ocamllex to lex one
>token at a time.
>
>Finally -- since your tutorial is Ocaml specific,
>I'd like to see some information on lexbufs.
>Are they functional? Can I write a backtracking
>functional parser that just 'goes backwards'
>in the input stream using a lexbuf to allow
>re-lexing some input? 
>
>How do i cope with the fact
>that lexbufs think they're reading named
>files with lines in them .. what if this isn't so?
>
>This is actually a design fault which is unfortunately
>propagated to Ocamlyacc.
>
>  
>


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-- 
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Erik de Castro Lopo
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