From: Kristof Bastiaensen <kristof@...>
Date: 2004-04-09T10:04:26+09:00
Subject: new method(?) collect_by

Hi, I have written a method collect_by.
I am not sure if it already exist, but it is very
usefull.  It is a generic version of collect, that
works with any method.  Basicly it converts the output
of any block to an Array

class Object
  def collect_by(method, *args)
    a = []
    send(method, *args) { |*o|
      a.push(block_given? ?
	     (yield *o) :
	     (o.size > 1 ? o : o[0])) }
    return a
  end
end

Examples:

"a string".collect_by(:each_byte)
=> [97, 32, 115, 116, 114, 105, 110, 103]

3.collect_by(:step, 20, 4)
=>[3, 7, 11, 15, 19]

(3..7).collect_by(:each_with_index)
=> [[3, 0], [4, 1], [5, 2], [6, 3], [7, 4]]

5.collect_by(:times) { rand 100 }
=> [61, 85, 13, 52, 47]

5.collect_by(:times) { |i| i * i }
=> [0, 1, 4, 9, 16]