From: dblack@...
Date: 2006-07-07T19:59:43+09:00
Subject: Re: Regexp

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Hi --

On Fri, 7 Jul 2006, Pe=C3=B1a, Botp wrote:

> fr fred:
> # When I try this :
> #
> #  @a =3D "blabla1 blabla1 <math>test1<\math> blabla2 blabla2
> # <math>test2<\math>"
> #  @b =3D @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 ?
>
> your code works fine here,
>
> irb(main):001:0> @a =3D "blabla1 blabla1 <math>test1<\math> blabla2 blabl=
a2
> irb(main):002:0" <math>test2<\math>"
> =3D> "blabla1 blabla1 <math>test1<math> blabla2 blabla2 \n<math>test2<mat=
h>"
> irb(main):003:0> @b =3D @a.gsub(/<math>.+<\math>/,'ok')
> =3D> "blabla1 blabla1 ok blabla2 blabla2 \nok"
>
> (ignore the newline; i just copiednpaste fr your email...)

Interesting -- it actually works only *because* of the newline :-)
With the newline, the .+ starts again on the second line (since .
doesn't match a newline).  Without it, the greed of .+ consumes
everything up to the second <\math>.

So if it's really on two lines, the non-greedy .+ isn't needed.  But
it's probably a good idea anyway, as it will work in a larger number
of cases.


David

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  Complete foreword & sample chapters at http://www.manning.com/black!
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