From: Joey Zhou <yimutang@...>
Date: 2011-12-12T18:42:57+09:00
Subject: [ruby-core:41605] [ruby-trunk - Feature #5749] new method String#match_all needed


Issue #5749 has been updated by Joey Zhou.


Yui NARUSE wrote:
> Why don't you use $~, $&, $`, $', $+, $1, $2, .. in scan' block parameter?

You reminds me! Yes, what I want can be done in this tricky way. Thank you!

However, I think relying on these special global variables is just an expedient.

If there is an explicit method, it's much more user-friendly and readable.

When I wanted the function, what I did is to consult the API, attempting to find a proper method, not thinking how to play with those magic punctuation. Maybe most people is just like me...


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Feature #5749: new method String#match_all needed
http://redmine.ruby-lang.org/issues/5749

Author: Joey Zhou
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


The String class should contain an instance method 'match_all', which is a mixture of 'match' and 'scan'.

The method 'scan' is not a very powerful tool, its result(the yielding thing) is just a matched string or an array of captured strings.

p 'a1bc2de3f'.scan(/(.)\d(.)/) # [["a", "b"], ["c", "d"], ["e", "f"]]

If the regex argument contains groups, I even cannot get the whole matched string, and no information about the matched offsets.

So, a 'match_all' is very necessary. It scan the string, finding every matched, and yielding *MatchData instance* to the following block.

Here's a simple implemention in Ruby:

class String
  def match_all(re,i=0)
    if block_given?
      while m = self.match(re,i)
        yield m
        i = m.end(0)
      end
      return self
    else
      ary = []
      while m = self.match(re,i)
        ary << m
        i = m.end(0)
      end
      return ary
    end
  end
end

However, it is not efficient in the 'while m = self.match(re,i)' way, because it scan the string again and again. If string is UTF8-encoded and contains out-of-ASCII characters, I'm afraid getting the start index of it is so expensive.

So, I think a built-in 'match_all' method, which behaves just like 'scan' but yield MatchData, is needed.

Please consider it, thank you!


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