From: Pierre-Charles David <pcdavid@...>
Date: 2003-10-02T22:26:17+09:00
Subject: Support for arbitrary iterators in Enumerable?


Hello,

I really like the way Ruby handles iteration (each/yield), and
combined with all the standard methods in Enumerable, it makes it easy
powerful algorithms in a very concise way. However, and unless I'm
missing something, Enumerable is hard-coded to only use the standard
#each iterator.

Sometimes it's convenient for a class to provide several iterators.
For example, String has #each_line and #each_byte, and we could
imagine #each_word, #each_paragraph, etc. With the current setup, only
one of these can be aliased to #each and conveniently use
Enumerable#collect and friends.

I would really like to be able to pass the name of an iterator method
to Enumerable methods. If the parameter value defaults to :each, it
would not break any existing code.

Here's an example of what I'm thinking of, for Enumerable#collect:

module Enumerable
  def collect(iterator = :each)
    raise "Invalid iterator" if not self.respond_to?(iterator)
    result = Array.new
    self.send(iterator) do |val|
      result << yield(val)
    end
    return result
  end
end

Is this kind of thing already possible (maybe in 1.8.0) ? If not, do
you think it would be a valuable addition ?

-- 
Pierre-Charles David (pcdavid <at> emn <dot> fr)
Computer Science PhD Student, �cole des Mines de Nantes, France
Homepage: http://pcdavid.net/