From: Phrogz <phrogz@...>
Date: 2007-09-19T07:45:04+09:00
Subject: Re: Regexp help

On Sep 18, 4:04 pm, Jeremy Woertink <jeremywoert...@gmail.com> wrote:
> Daniel Lucraft wrote:
> > Jeremy Woertink wrote:
> >> What I want to do is determine if a string includes 2 special characters
> >> a semi-colon and a question mark.
>
> > You don't need regular expressions to do that, try this instead:
>
> > irb> encoding.include? ";" and encoding.include? "?"
> >   => true
>
> > On the other hand, if you want to use regular expressions regardless,
> > you should notice that String#include? takes a string rather than a
> > Regexp.
>
> > Note that:
> > irb> %r{;\?}.to_s
> >    > "(?-mix:;\\?)"
>
> > So
> > encoding.include?(%r{;\?}.to_s)
>
> > is equivalent to
> > encoding.include?("(?-mix:;\\?)")
>
> > which is not going to succeed.
>
> > To use a regexp, try:
> > irb> encoding =~ /(;.*\?)|(\?.*;)/
> >   => true.
>
> > best
> > Dan
>
> Thanks for the help. I would like to use a regexp becuase I think it
> will look nicer in the code. I tried your example and got
>
> C:\rails_apps\hotswipe>irb
> irb(main):001:0> require 'config/environment'
> => true
> irb(main):002:0> encoding = ";6277200301500269=?"
> => ";6277200301500269=?"
> irb(main):003:0> encoding =~ /(;.*\?)|(\?.*;)/
> => 0
> irb(main):004:0>
>
> So what does the 0 mean? 0 matches? If all else fails, I will use the
> ugly version :)

It means that it found the first match starting at index 0 in the
string. (Try reading the documentation on the =~ method.)

Note that the supplied regexp will fail if your string has a newline
in it. You may want to append the 'm' (multiline) modifier to it, e.g.
  /;.*\?|\?.*;/m
(There's also no need for the parentheses, and a minor theoretical
speed/memory reason to leave them off.)