From: Dominic Fox <dominic.fox@...>
Date: 2002-10-07T00:34:12+09:00
Subject: Block Puzzle

Hello Ruby list!

I have recently started playing with Ruby, and I'm currently being 
puzzled by something that doesn't work the way I expect it to. Here's an 
example script:

# A function that yields the double of each member of a list

def doubleMe(list)
  list.each do |value|
    yield value * 2
  end
end

# A function that yields values 1-5

def yieldValues
  yield 1
  yield 2
  yield 3
  yield 4
  yield 5
end

# A list

myList = [1, 2, 3, 4, 5]

# Yield double the value of each item in my list to a block which says
# something nice about Ruby - works.

doubleMe(myList) { |value| puts "#{value} reasons to love Ruby" }

# Define a Proc object which does the same as the block above

outPutter = proc do |value|
  puts "#{value} reasons to love Ruby"
end

# Use the Proc object as the block for function yieldValues - works.

yieldValues &outPutter

# Modify the Array class to include an "eachDouble" method

module Doubler
  def eachDouble
    each do |value|
      yield value * 2
  end
  end
end

class Array
  include Doubler
end

# Use the Proc object as a block for this new method - works.

myList.eachDouble &outPutter

# Doesn't work. Why?

doubleMe(myList) &outPutter

---

Can anyone shed any light on why the final line in this script produces 
an error?

thanks,
Dominic