From: Nate Wiger <nwiger@...>
Date: 2006-10-21T06:57:08+09:00
Subject: Re: Easy way to check is sub!() succeeds?

Gavin Kistner wrote:
>> But sub! always returns nil, even when it succeeds (in Perl, it will 
>> return the number of substitutions made, enabling "next if 
>> s/\.$suf$//")
> 
> Er, no it doesn't.
> 
> irb(main):001:0> s="aaabbb"
> => "aaabbb"
> irb(main):002:0> s.sub!(/a+/,'')
> => "bbb"
> irb(main):003:0> s.sub!(/zzz/,'')
> => nil

Ok, that makes more sense. Turns out I was upsetting Ruby's 
scoping/aliasing. Eventually I got an error "Can't modify frozen 
string", which tipped me off. Now I have:

    ARGV.each do |file|
       path = file.dup   # copy to tweak
       zip.each do |suf, cmd|
          if path.sub!(%r{\.#{suf}$}, '')

And everything works ok. Seems like a loop w/i a loop thing? Anyways, 
thanks for the sub!() ptr.

-Nate