From: Martin Elzen <martinelzen@...>
Date: 2004-04-30T22:28:47+09:00
Subject: Why is regexp "\Amax_repeats=(\d+)" not equal to "^max_repeats=([0-9]+)" ?


Hi everyone.

I'm trying to learn how to program in Ruby, and yesterday I came across a 
Regexp issue I can't figure out.  I want to parse a commandline argument of 
the form: max_repeats=<integer>

After studying the 'pick-axe' book, I came up with the line:
regexp = Regexp.new("\Amax_repeats=(\d+)")

but the above regexp fails to match with correct input.  When I changed that 
line to the following:
regexp = Regexp.new("^max_repeats=([0-9]+)")

it *does* match correctly with the proper input.

What I would like to know is, why doesn't the first Regexp work?  (FWIW, I'm 
using Ruby 1.8.1 on Win2003 server.)

Sincerely,
Martin

PS a complete program with my regexp matching code is as follows:

#define globals

$max_repeat_count_default = 5




def get_max_repeats_value
  result = $max_repeat_count_default

  if not ARGV.empty?

    #regexp = Regexp.new("\Amax_repeats=(\d+)")
    #@@@
    regexp = Regexp.new("^max_repeats=([0-9]+)")

    matchdata = candidate_val = match_val = nil

    ARGV.each do |arg|
      matchdata = regexp.match(arg)

      if matchdata != nil
        match_val = matchdata[1].to_i

        if candidate_val == nil
          candidate_val = match_val
        else
          candidate_val = match_val if match_val > candidate_val
        end

      end

    end

    result = candidate_val if candidate_val != nil and candidate_val > 0

  end

  result
end



begin
  max_repeats = get_max_repeats_value
  puts "max_repeats=" + max_repeats.to_s

  rescue Exception => ex
    print "Exception exception: " + ex.message +
          ",\nbacktrace:\n" + ex.backtrace.join("\n")

end

_________________________________________________________________
Hotmail en Messenger on the move 
http://www.msn.nl/communicatie/smsdiensten/hotmailsmsv2/