From: dblack@...
Date: 2003-01-11T06:30:38+09:00
Subject: Re: regexp question

Hi --

On Sat, 11 Jan 2003, Mark Probert wrote:

>
> Hi, again, Rubyists.
>
> Below is code that does multiple substitutions on a block of
> text, using a recursive call to a regexp.  The output is like:
>
>    s1 = {\aa TEXT:}  It is {\bb amazing} what a {\xx regexp} can do
>    s2 = <alpha>TEXT:</alpha>  It is <beta>amazing</beta> what a
> <xx>regexp</xx> can do
>
>
> The trouble is I am getting the following warning (repeated 3 times)
>
>    warning: string pattern instead of regexp; metacharacters no longer
> effective
>
> when I run the code. The warning comes from the line in the code that reads
>
>    s = str.sub(match[0], ssub)
>
> This expression works (no warnings) outside the function.  Any ideas as to
> why this is happening and how I can get around the warning?

I couldn't quite get your code to run, and sort of rewrote it (see
below).  But in general, that warning has to do with a recent change
in metacharacter handling in cases where an argument can be either a
string or a regex, and I'm pretty sure the warning will only exist for
one version or so of Ruby, and then be taken out.

> BTW, is the a better way of doing this task?

I would use String#gsub:

  subs = { "aa" => "alpha",
	   "bb" => "beta" }

  s1 = '{\aa TEXT:}  It is {\bb amazing} what a {\xx regexp} can do'
  s2 = s1.gsub(/\{\\(\S+)\s([^}]*)\}/) do |s|
    tag = subs[$1] || $1
    "<#{tag}>#{$2}</#{tag}>"
  end

  puts "s1 = #{s1}"
  puts "s2 = #{s2}"


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav