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comp.lang.ruby

using variables in regular expressions

Vassilis Rizopoulos

11/24/2003 2:06:00 PM

Being lazy, forgetful and generally very bad with regular expressions
leads me to post this question:

How can I use the contents of a variable as a pattern in a regular
expression?

I get a list of files from a set of paths and I want to do the following

repo=list_files paths
repo.collect!{|entry|
entry.gsub(/{variable_with_the root_I_want_to_substitute}/,"")
}

pretty straightforward no?
V.-



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3 Answers

Robert Klemme

11/24/2003 4:30:00 PM

0


"Damphyr" <damphyr@freemail.gr> schrieb im Newsbeitrag
news:3FC2104E.7080607@freemail.gr...
> Being lazy, forgetful and generally very bad with regular expressions
> leads me to post this question:
>
> How can I use the contents of a variable as a pattern in a regular
> expression?
>
> I get a list of files from a set of paths and I want to do the following
>
> repo=list_files paths
> repo.collect!{|entry|
> entry.gsub(/{variable_with_the root_I_want_to_substitute}/,"")
> }

using gsub! is more efficient and better use %r{} because Regexp.quote
does not quote "/":

repo=list_files paths
repo.each {|entry|
entry.gsub!(%r{#{Regexp.quote(variable_with_the
root_I_want_to_substitute)}},"")
}

Regards

robert

sabbyxtabby

11/25/2003 6:51:00 PM

0

"Robert Klemme" <bob.news@gmx.net> wrote:

> "Damphyr" <damphyr@freemail.gr> schrieb im Newsbeitrag
> news:3FC2104E.7080607@freemail.gr...
> >
> > repo.collect!{|entry|
> > entry.gsub(/{variable_with_the root_I_want_to_substitute}/,"")
> > }
>
> using gsub! is more efficient and better use %r{} because Regexp.quote
> does not quote "/":
>
> repo.each {|entry|
> entry.gsub!(%r{#{Regexp.quote(variable_with_the
> root_I_want_to_substitute)}},"")
> }

Don't need %r{}. A slash "/" in interpolated variables is harmless.
Add anchor, unless removing root from middle of path is desirable.
Add /o modifier:

entry.gsub!(/^#{Regexp.quote(root)}/o, "")

Robert Klemme

11/26/2003 8:52:00 AM

0


"Sabby and Tabby" <sabbyxtabby@yahoo.com> schrieb im Newsbeitrag
news:f5a79bf2.0311251050.1cb4c32d@posting.google.com...
> "Robert Klemme" <bob.news@gmx.net> wrote:
>
> > "Damphyr" <damphyr@freemail.gr> schrieb im Newsbeitrag
> > news:3FC2104E.7080607@freemail.gr...
> > >
> > > repo.collect!{|entry|
> > > entry.gsub(/{variable_with_the root_I_want_to_substitute}/,"")
> > > }
> >
> > using gsub! is more efficient and better use %r{} because Regexp.quote
> > does not quote "/":
> >
> > repo.each {|entry|
> > entry.gsub!(%r{#{Regexp.quote(variable_with_the
> > root_I_want_to_substitute)}},"")
> > }
>
> Don't need %r{}. A slash "/" in interpolated variables is harmless.

True.

> Add anchor, unless removing root from middle of path is desirable.

I had that in my first version, but apparently the "^" didn't make it into
the posting. Thx!

> Add /o modifier:

I wouldn't do that if the rx was in a method that received the path as
parameter. Could lead to surprising effects. :-)

> entry.gsub!(/^#{Regexp.quote(root)}/o, "")

Cheers

robert