From: Simon Strandgaard <neoneye@...>
Date: 2004-04-12T22:49:14+09:00
Subject: Re: zip block oddities/bug?

On Mon, 12 Apr 2004 07:42:35 +0100, daz wrote:
[snip] 
> Since an array is deliberately *not* being built, what
> could usefully be returned outside the block ?
> ("nil" seems like a good choice).
> 

zip should simply just concatenate the data it gets back from
the block.

I have made a pseudo-implementation, where blocks is working.
It differs sligthly from the real zip, because I am cheating
and using the :[], rather than each.

server> ruby a.rb
[["a"], ["b"], ["c"]]
[["a", 1, 3, 1], ["b", 2, 4, 1], ["c", nil, 5, 1], ["d", nil, 6, 0]]
[[4, 1, "a"], [5, 1, "b"], [nil, 0, "c"]]
[[0, :lo], [1, :lo], [2, :hi], [3, :hi], [4, :hi]]
[9, "a", 8, "b", 7, "c"]
server> expand -t2 a.rb 
module Enumerable
  def zip2(*args)
    res = []
    self.each_with_index do |element, index|
      data = [element] + args.map{|i| i.respond_to?(:[]) ? i[index] : i}
      res += block_given? ? yield(data) : [data]
    end
    res
  end
end
p %w(a b c).zip2
p %w(a b c d).zip2([1, 2], [3, 4, 5, 6], 7)
p %w(a b c).zip2(3, [4, 5]) {|i| [i.reverse]}
p (0..4).zip2 {|i| [i << (i[0] < 2 ? :lo : :hi)]}
p %w(a b c).zip2([9, 8, 7]) {|i| i.reverse}
server>

It wakes memories of inject.

--
Simon Strandgaard