From: Brian Candler <B.Candler@...>
Date: 2003-05-25T01:42:22+09:00
Subject: Re: why is "does" missing from this sub!-stitution?

On Sat, May 24, 2003 at 10:23:22AM +0900, dblack@superlink.net wrote:
> So the order of things seems a little odd:
> 
>   /(..)/.match("abcdef")        # match operation, $1 set
>   "abcdef".sub(/(..)/, "#$1")   # match operation, $1 *not* set
>                                   then string parsed,
>                                   *then* $1 is set

In the second case, /(..)/ simply creates a Regexp object, like
Regexp.new("(..)"). It does not match it against anything.

This regexp is passed as a parameter to sub; it is inside sub that the
regexp is actually used.

You could write it like this:

   class String
     def mysub(regexp, newstr)
       if regexp =~ self
         return $` + newstr + $'
       end
       self
     end
   end
   "abcdefabcdef".mysub(/de/,'zz')  #>> "abzzefabcdef"

(except to get the full functionality, after doing the match you'd replace
'\' '1' in newstr with the contents of $1, '\' '2' with $2, etc)

Regards,

Brian.