From: Caleb Clausen <vikkous@...>
Date: 2005-08-02T02:07:33+09:00
Subject: Re: Redefining Regexp#===

On 8/1/05, Pit Capitain <pit@capitain.de> wrote:
> Hi,
> 
> what's wrong with this code:
> 
>    class Regexp
>      alias :case_eq :===
>      def ===( other )
>        case_eq( other )
>      end
>    end
> 
>    p( /x/ === "abxy" )         # => true
>    p( Regexp.last_match )      # => nil
>    p( /x/.case_eq( "abxy" ) )  # => true
>    p( Regexp.last_match )      # => #<MatchData:0x2a67460>
> 
> Why is Regexp.last_match not set when calling the redefined method?
> This is ruby 1.8.2 (2004-12-25) [i386-mswin32] on Windows 2000.

I have discovered that $1 and the like and Regexp.last_match behave
differently than I expected. These all behave like local variables in
the method that calls the Regexp matching method, even tho they look
like global variables and a class method.

Your === doesn't work the expected way because it's no longer the
magical built-in version, which exports the local variables $1 and
friends and Regexp.last_match to it's immediate caller.

I don't think there's a way to workaround this behaviour. This is bad
actually; it means there's no safe way to override Regexp#===,
Regexp#match, etc safely, so that the callers still have all the same
old behaviour.

Regexp#last_match cannot be usefully overridden because you can't call
the original method in the override to retrieve the MatchData... it
ends up always nil.

I really hope the current behavior can be changed..... I need to be
able to override === and match safely. Can't these variables be made
thread globals instead of locals? Or at least provide a way to
re-export the matching local vars to your own caller? Or actually be
able to overrride Regexp.last_match?

Ps: why do you want this?