From: "David A. Black" <dblack@...>
Date: 2005-05-18T22:19:13+09:00
Subject: Re: Variable substitution in a regex

Hi --

On Wed, 18 May 2005, Steve Callaway wrote:

> Yeah, straightforward enough, moreover you can process
> an array of vars as in the snippet I put up on
> Rubyforge:
>
> # function to regexp vars
> def is_element_in_string?(in_string, in_array)
> in_array.each do |line|
> rx_test = /#{line}/
>            if  in_string =~ rx_test
>                             return true
>            end
> end
> return false
> end

Let Ruby do the work for you :-)

   def is_element_in_string?(str, elements)
     elements.any? {|e| /#{e}/.match(str) }
   end

> # as an example we may wish to see whether a list of
> football match results
> # contains a result of a team we are interested in
> varray = Array.new
> # now populate the array with reegxps you wish to
> match...
> varray = ["Plymouth Argyle", "Blackburn Rovers" ,
> "Manchester .*", "Tott.*"]

You're not populating the array; you're discarding the array and
creating a completely new one :-)  The array you created previously
ceases to exist.

You can either just leave out that first assignment, or if you have
some reason to create and populate the array in two steps, you could
do:

   varray = Array.new
   varray.replace(["Plymouth ...", "...", ...])

but I can't think of any reason to do that.  I would just assign the
array to the variable, as in your second assignment.


David

-- 
David A. Black
dblack@wobblini.net