Sample functions for String Parsers in Lisp

Sample functions for String Parsers in Lisp

[Nordlöw]

Has anybody any good sample code in elisp that shows how to
conveniently do parsing of code contained in a string?

Reason: I am writing a parser that converts Emacs regexps (back) into
rx expressions. I need this for my file magic pattern matcher in order
to read as little data as possible from the file (locality) and do
several matchings in parallel.

I think the main loop should be string-iteration-driven using while()
and aref() and length() I presume.

Any suggestions?,
Nordlöw

Re: Sample functions for String Parsers in Lisp

[Pascal J. Bourguignon]

Nordlöw <per.nordlow@gmail.com> writes:

> Has anybody any good sample code in elisp that shows how to
> conveniently do parsing of code contained in a string?
>
> Reason: I am writing a parser that converts Emacs regexps (back) into
> rx expressions. I need this for my file magic pattern matcher in order
> to read as little data as possible from the file (locality) and do
> several matchings in parallel.
>
> I think the main loop should be string-iteration-driven using while()
> and aref() and length() I presume.
>
> Any suggestions?,

1- Read the Dragon Book.
   http://www.amazon.com/Compilers-Principles-Techniques-Alfred-Aho/dp/0201100886

2- Use a parser generator.  
   http://cedet.sourceforge.net/info/semantic.html


-- 
__Pascal Bourguignon__

Re: Sample functions for String Parsers in Lisp

[Helmut Eller]

* Pascal J. Bourguignon [2009-10-13 14:47+0200] writes:

> Nordlöw <per.nordlow@gmail.com> writes:
>> Any suggestions?,
>
> 1- Read the Dragon Book.
>    http://www.amazon.com/Compilers-Principles-Techniques-Alfred-Aho/dp/0201100886
>
> 2- Use a parser generator.  
>    http://cedet.sourceforge.net/info/semantic.html

3. Use parsing expression grammars:
http://www.emacswiki.org/emacs/peg.el

Helmut

Re: Sample functions for String Parsers in Lisp

[Andreas Politz]

Nordlöw <per.nordlow@gmail.com> writes:

> Reason: I am writing a parser that converts Emacs regexps (back) into
> rx expressions. I need this for my file magic pattern matcher in order
> to read as little data as possible from the file (locality) and do
> several matchings in parallel.
>
[...]

> Any suggestions?,
> Nordlöw

Yes, save yourself the headache and make the assumption, that all magic
pattern are fully contained in the first n bytes of the file.

-ap

Re: Sample functions for String Parsers in Lisp

[LanX]

> Any suggestions?,
> Nordlöw

Do you speak Perl?

If yes you may wanna have a look at the structure of the YAPE module
and try to port the parser.

http://search.cpan.org/dist/YAPE-Regex-Explain/Explain.pm

IMHO you just have to get alog with the backslasheritis of elisp...

Good luck
  Rolf