From: Kenneth McDonald <kenneth.m.mcdonald@...>
Date: 2006-10-13T14:17:04+09:00
Subject: Re: Ruby equivalent of assemble RE?

James Edward Gray II wrote:
> On Oct 12, 2006, at 5:47 PM, John Ky wrote:
>
>> Is there a ruby equivalent of this?
>>
>> http://search.cpan.org/dist/Regexp-Assemble/Assemble.pm
>
> I'm not aware of one, though we did play with the idea a little in a 
> very old Ruby Quiz:
>
> http://www.rubyquiz.com/quiz4.html
>
> At 3,000 lines (granted a lot of that is documentation), it's a hefty 
> port job.  I think it's a neat library though.  Would be cool to see 
> it done.
>
> James Edward Gray II
>
>
If what you want is a way to easily assemble and use regular 
expressions, I have a Python library that comes in at about 700-800 
lines (excluding unit tests and docs). For example, to define a re 
matching integer complex numbers (uses the fact that Python allows 
named, not just numbered, re groups):

  intPat = OPT("-") + CHAR("0123456789")*1       # *1 means 1 or more.
  complexPat = intPat['real'] + ALT("-", "+")['op'] + intPat['im']

Let's find out the real parts of all complex numbers in a string:

  for matchresult in complexPat.iter(somestring): print matchresult['real']

Using some of the package's predefined patterns, let's define a complex 
num pattern that handles floating point numbers and whitespace:

  complex = PAT.float['real'] + CHAR.whitespace*0 + ALT("-", "+")['op'] 
+ PAT.float['im']

etc. etc. I'd like to convert it to Ruby, but don't have the time. It'd 
be a significant but not huge job--more tedious than anything else. I 
suspect the Ruby version would come in a little shorter, maybe 600 
lines? Anyone interested?


Ken