From: Stefan Rusterholz <apeiros@...>
Date: 2008-12-11T17:44:43+09:00
Subject: Re: lambda with $1 fails as gsub block

Mike Gold wrote:
> 
> I came across this problem:
> 
>   def meth(replace)
>     ">x".gsub(%r!(\W)x!, &replace)
>   end
> 
>   replace = lambda { |match|
>     puts "$1 is #{$1.inspect}"
>   }
> 
>   ">x".gsub(%r!(\W)x!, &replace)  # => $1 is ">"
> 
>   "" =~ %r!!  # reset $1
> 
>   meth(replace)  # => $1 is nil
> 
> Apparently $1 is bound in a peculiar way:

Interesting issue. A work-around:
module MDGsub
  def md_gsub(pattern)
    gsub(pattern) { yield($~) }
  end
end
class String
  include MDGsub
end

block = proc { |md| p [md.string, *md.captures] }
 ">x".md_gsub(%r!(\W)x!, &block)  # -> [">x", ">"]

I hope that helps for the moment.

Regards
Stefan
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