From: "Bartosz Dziewoński" <matma.rex@...>
Date: 2011-08-29T16:24:00+09:00
Subject: Re: String#split resets regex captures variables (Ruby 1.8.7)

I think it makes sense for $1, $2 etc to change any time a regex match
is performed anywhere in Ruby, it might be even kind of useful in some
perverse scenarios. That said, you shouldn't use these if you can,
it's a Perl relic (but I admit, sometimes it's the easiest way).

There are two solutions: either bind their values to another variables:

 n = "a:c"
 if n =~ /([a-z])([.:])([a-z])/
  sep = $2
  p [:first, :second].zip(n.split(sep)) | [[:separator, sep]]
 end

or use #match like a man:

 n = "a:c"
 if mtc = n.match(/([a-z])([.:])([a-z])/)
  p [:first, :second].zip(n.split(mtc[2])) | [[:separator, mtc[2]]]
 end



-- Matma Rex



2011/8/29 7stud -- <bbxx789_05ss@yahoo.com>:
> Olivier Lance wrote in post #1018967:
>> Hi,
>>
>> I've just spent some time on this problem until I found the solution,
>> and I wanted to share it/ask for opinions on this:
>>
>> I've got a string on which I try to match a regexp. If it matches, I
>> split the string with one of the captured groups, zip the resulting
>> array with an array of symbols and merge with a last symbol/string array
>> pair representing the captured separator.
>>
>> Here's some code to give you an idea:
>>
>> n = "a:c"
>> if n =~ /([a-z])([.:])([a-z])/
>>   p [:first, :second].zip(n.split($2)) | [[:separator, $2]]
>> end
>>
>> (see pastie here: http://pastie.org/2445983)
>>
>
> Do you actually consider that a lucid example of the problem?  Bejeesus.
>
>>
>> The problem is, the resulting array will contain "nil" for :separator.
>> Apparently, String#split will reset all regexp-related variables... I
>> guess it uses regexp internally, but I haven't seen anything documenting
>> this behavior, and I honestly believed this code would work...
>>
>> So what's your take on this? Does it feel natural/logical to you?
>> Should I file a bug to enhance Ruby's documentation?
>
>
> $ cat ruby.rb
> str = 'abcd'
>
> if str =~ /(c)(d)/
>  p [$1, $2]
>  str.split('b')
>  p [$1, $2]
> end
>
> $ multiruby ruby.rb
> /Users/me/.rvm/gems/ruby-1.9.2-p180@rails3tutorial/gems/ZenTest-4.5.0/lib/multiruby.rb:330:
> warning: shadowing outer local variable - s
> /Users/me/.rvm/gems/ruby-1.9.2-p180@rails3tutorial/gems/ZenTest-4.5.0/lib/multiruby.rb:391:
> warning: shadowing outer local variable - s
>
> VERSION = 1.8.6-p420
> CMD     = ~/.multiruby/install/1.8.6-p420/bin/ruby ruby.rb
>
> ["c", "d"]
> [nil, nil]
>
> RESULT = pid 3744 exit 0
>
> VERSION = 1.8.7-p352
> CMD     = ~/.multiruby/install/1.8.7-p352/bin/ruby ruby.rb
>
> ["c", "d"]
> [nil, nil]
>
> RESULT = pid 3745 exit 0
>
> VERSION = 1.9.1-p431
> CMD     = ~/.multiruby/install/1.9.1-p431/bin/ruby ruby.rb
>
> ["c", "d"]
> ["c", "d"]
>
> RESULT = pid 3746 exit 0
>
> VERSION = 1.9.2-p290
> CMD     = ~/.multiruby/install/1.9.2-p290/bin/ruby ruby.rb
>
> ["c", "d"]
> ["c", "d"]
>
> RESULT = pid 3747 exit 0
>
> TOTAL RESULT = 0 failures out of 4
>
> Passed: 1.8.6-p420, 1.8.7-p352, 1.9.1-p431, 1.9.2-p290
> Failed:
> $
>
> --
> Posted via http://www.ruby-forum.com/.
>
>