Re: Guile regular expressions are too greedy

[Chris Dennis <cgdennis@btinternet.com>]

Ludovic Courtès wrote:
> Hello,
> 
> Chris Dennis <cgdennis@btinternet.com> writes:
> 
>> Hello Guile People
>>
>> Is there a way to make Guile regular expressions less greedy?  I
>> understand that POSIX doesn't define non-greedy modifiers.
>>
>> Specifically, I'm trying to parse font names such as
>>
>>     Arial 12
>>     Arial Bold Italic 14
>>     Nimbus Sans L Bold Italic Condensed 11
>>
>> so that I can construct CSS styles from them.
>>
>> I've tried the following, but the first (.*) gobbles up everything
>> before the size because the other elements are optional:
>>
>> (define s (string-match "(.*)( +(bold|semi-bold|regular|light))?(
>> +(italic|oblique))?( +(condensed))? +([0-9]+)" "nimbus sans l bold
>> italic condensed 11"))
> 
> Here's a possible solution:
> 
> --8<---------------cut here---------------start------------->8---
> scheme@(guile-user)> (define rx (make-regexp "^([^ ]+)( +(bold|semi-bold|regular|light))?( +(italic|oblique))?( +(condensed))? +([0-9]+)" regexp/extended))
> scheme@(guile-user)> (define m (regexp-exec rx "nimbus bold italic condensed 11"))
> scheme@(guile-user)> (match:substring m 1)
> "nimbus"
> scheme@(guile-user)> (match:substring m 2)
> " bold"
> scheme@(guile-user)> (match:substring m 3)
> "bold"
> scheme@(guile-user)> (match:substring m 4)
> " italic"
> scheme@(guile-user)> (match:substring m 5)
> "italic"
> --8<---------------cut here---------------end--------------->8---
> 
> Note that I slightly modified the string that's matched because "sans"
> and "l" are not meant to be matched.
> 
> Hope this helps,
> Ludo'.

Thanks for the reply.

Unfortunately the name of the font really is "Nimbus Sans L" -- it's the 
fact that font names can contain spaces that causes the problem, and 
means that I can't use ([^ ]+) to match the font name.

cheers

Chris

-- 
Chris Dennis                                  cgdennis@btinternet.com
Fordingbridge, Hampshire, UK