Re: [q-lang-users] silly regex wonderings

[<Dr....@t-...>]

Hi, David!

> BTW, Hi there.
> I'm a maths student, I've been lurking here a while and I just finished my
> exams
> for the year, which gives me more time to play with Q and other nice things

So welcome to the list, and thanks for helping out. How do you like Q so 
far? ;-)

> OK, you've got me playing with these regexes now.
> 
> Based on the regsplit example, a regex search and replace is:
> 	snr Opts OldRE NewRE S = strcat
> 		(regex Opts OldRE S (regskip ++ `NewRE)
> 		++ [regskip]);

This is cute. I'd like to add this to the examples in the docs, ok?

BTW, to make it even prettier, you could declare snr as a special form 
like so:

special snr ~Opts ~OldRE NewRE ~S;

snr Opts OldRE NewRE S = strcat
		(regex Opts OldRE S (regskip ++ NewRE)
		++ [regskip]);

Then you don't need the backquote/quote magic. E.g.:

embolden2 = snr "g" "\\*([^\\*]*)\\*" (tag "bold" (reg 1));

tagify Delim Tag = snr "g" (Delim++"([^"++Delim++"]*)"++Delim)
		   (tag Tag (reg 1));

This works because the evaluation of the NewRE argument of snr is now 
deferred until it is used on the rhs of the snr definition.

> The problem is 
> ==> underline (embolden3 "This has *bold _underlining*_ !")
> "This has <bold>bold <underline>underlining</bold></underline> !"

Yes, you're right, to properly handle this case you'd need a 
context-free parser. This is an area where Q is still lacking. Hmm, is 
there someone here who knows Haskell's parser combinator library 
reasonably well? Maybe we could port some of this stuff to Q. Writing 
some kind of Q lex/yacc would also be an interesting project. Anyone 
interested?

Cheers,
Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikwissenschaft.uni-mainz.de/~ag