From: dblack@...
Date: 2006-07-07T19:54:06+09:00
Subject: Re: Regexp

Hi --

On Fri, 7 Jul 2006, Fred VD wrote:

> Hello,
>
> I'm new to Ruby and I'm fighting with regexp.
>
> I would like to replace '<math>test1<\math>' and '<math>test2<\math>' by
> 'ok' in the string "blabla1 blabla1 <math>test1<\math> blabla2 blabla2
> <math>test2<\math>"
>
> When I try this :
>
> @a = "blabla1 blabla1 <math>test1<\math> blabla2 blabla2
> <math>test2<\math>"
> @b = @a.gsub(/<math>.+<\math>/,'ok')
>
> I get "blabla1 blabla1 ok" instead of "blabla1 blabla1 ok blabla2
> blabla2 ok"
>
> Could you please help me to tune my regexp so it works the way I want ?

As I suspect seven or eight people will tell you, you need to make
your one-or-more quantifier non-greedy :-)  Note the question mark:

   a = "blabla1 blabla1 <math>test1<\\math> blabla2 blabla2
   <math>test2<\\math>"
   puts a.gsub(/<math>.+?<\\math>/,'ok')

I've made a couple of other changes.  In a double-quoted string, "\m"
is just the letter m.  If you want a \ you have to escape it with
another \.  (Are you sure you don't want a forward slash anyway?)

I have a feeling you don't really need instance variables here; if
not, it's better to use locals.


David

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