From: dblack@...
Date: 2002-11-12T22:36:34+09:00
Subject: Re: ruby-dev summary 18613-18710

Hi --

On Tue, 12 Nov 2002, TAKAHASHI Masayoshi wrote:

> Hi all,
>
> One of the happiest things for me in RubyConf2002 was
> to meet readers of this summary.  Thanks again!

It was good to see you again -- looking forward to next year!

> [ruby-dev:18651] Enumerable#zip
>
>   Matz implemented Enumerable#zip method, but he has not
>   decide its behavior yet.
>
>   Enumerable#zip is a method to mix some sequences(Array or
>   Object which has to_ary method). But, when length of
>   sequences are not same, the behavior is not clear.

[...]

>
>     a = [1,2,3,4]
>     b = [2,4]
>     a.zip(b) #=> ?

>    c.) a.zip(b) #=> [[1,2],[2,4],[3,nil],[4,nil]]
>        b.zip(a) #=> [[2,1],[4,2]]

That makes sense to me.  The iteration is over the receiver, so the
length of the result is the same as the length of the receiver.
Something like:

  module Enumerable
    def zip(other)
      (0...size).map {|i| [to_a[i],other.to_a[i]] }
    end
  end

(Of course it would look better if we had #map_with_indices :-)

I once wrote something called Array#braid, which zipped two or more
arrays:

  [1,2,3].braid([4,5,6],[7,8,9])

     # => [ [1,4,7], [2,5,8], [3,6,9] ]

Was there any discussion of a generalized version of zip?


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav