From: matz@... (Yukihiro Matsumoto)
Date: 2003-05-13T17:15:19+09:00
Subject: Re: [RCR?] Enumerable#each with arguments

Hi,

In message "Re: [RCR?] Enumerable#each with arguments"
    on 03/05/13, Sam Roberts <sroberts@uniserve.com> writes:

|Quoteing matz@ruby-lang.org, on Mon, May 12, 2003 at 12:14:46PM +0900:
|> Hmm, but some of enumerable methods take its own argument, for example
|> "grep".  In addition, class dependent additional argument breaks
|> polymorphism.  There must be better idea (e.g. external iterator object).
|
|Yes, but we *like* using each() rather than an external iterator!

Yes, but it is easy like this:

  # Enumerable extension.
  module Enumerable
    class Enumerator
      include Enumerable
      def initialize(obj, *args)
        @obj = obj
        @args = args
      end
      def each(&block)
        @obj.each(*@args, &block)
      end
    end
    def each_with(*args)
      Enumerator.new(self, *args)
    end
  end

  # sample class
  class Foo
    include Enumerable
    def each(n=100)
      for i in 0..n
        yield i
      end
    end
  end

  f = Foo.new
  f.each(5){|i| p i}
  f.each_with(5).collect{|i| i*3}


							matz.