From: Mark Hubbart <discord@...>
Date: 2004-04-14T07:59:13+09:00
Subject: Re: New Ruby questions...


On Apr 13, 2004, at 3:14 PM, Jeff Massung wrote:

> I've just started Ruby a couple days ago

welcome! :)

> 1. How can a regexp get the longer of two possibilities that are
> ambiguous? For example, I need to be able to strip out register names:
>
> registers = '(r0|r1|r2|r3...|r10|r11|r12...)'
>
> In the regular expression, how can I get it to find r10 or r11 instead 
> of
> stopping at r1? I get the same problem with opcode mnemonics (like B
> instead of BX or BL).

Are you wanting a regex that matches register names? here's a couple 
ways:

   # A bit lazy, but less complicated: matches 1 or 2 digit numbers
   # the \d means match any single digit; following the second \d with
   # a ? means that it should match it if it's there, but it is optional.
   register_regex = /r\d\d?/

   # A bit less more complex, but more precise; matches up to "r42"
   # rough translation: "match an 'r', followed by either the a digit
   # followed by a non-digit; or a number 1-3 followed by one digit
   # and a non-digit; or the number 4 followed by  a 0, 1, or 2.
   register_regex = /r(?:\d\D|[1-3]\d\D|4[012]\D)/

If you are going to  be doing lots of regex stuff, I highly reccoment 
going out and getting a small pocket manual regex reference. When I 
started working with them, I got a little perl-oriented one, but it 
works just as well for Ruby, PHP, or most other implementations. I just 
marked it up to show what was available in each language.

cheers,
--Mark