[Newbies] Re: Lookaround Regex to manipulate Strings

[Hans Gruber]

Hi Guys!

Thank you so much, this worked fine!

Regards,
Hans

> Hans Gruber wrote:
> > Hi Squeak Fans!
> > 
> > I have a short question regarding regular expressions in Squeak.
> > 
> > I have the following problem:
> > 
> > I have a fileName and I want to cut off its file extension (.jpg, .png etc.). To do this efficiently I wanted to use regular expressions with lookaround.
> 
> Using regular expressions may be convenient, it sure as hell isn't 
> efficient. Much easier to use, e.g.,
> 
>    fileName copyUpToLast: $.
> 
> As for efficiency:
> 
> [1 to: 10000 do:[:i|
> 	'filename.jpg' matchesRegex: '.+(=?.(jpg|jpeg|png))'
> ]] timeToRun.
> => 2222 msecs
> 
> [1 to: 10000 do:[:i|
> 	'filename.jpg' copyUpToLast: $.
> ]] timeToRun.
> => 30 msecs
> 
> So using regexp's is about 80x slower.
> 
> Cheers,
>    - Andreas
> 
> 
> > So let's assume the following:
> > 
> > | fileName |
> > fileName := 'test.jpg'.
> > 
> > fileName matchesRegex: '.+(=?.(jpg|jpeg|png))'
> > 
> > I thought there is a possibility of returning the string without file extension through lookaround.
> > 
> > Do you have any hints for me?
> > 
> > Thanks guys!
> > 
> > Regards,
> > Hans
> > ______________________________________________________
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> 
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