From: Wilson Bilkovich <wilsonb@...>
Date: 2007-01-17T02:32:37+09:00
Subject: Re: what is dup?

On 1/16/07, David Madden <moose56@gmail.com> wrote:
> I am playing with an example in the ruby cookbook where  a shuffle
> function is added to the array class:
>
> class Array
>
>    def shuffle!
>      each_index do |i|
>        j = rand(length-i) + i
>        self[j], self[i] = self[i], self[j]
>      end
>    end
>
>    def shuffle
>      dup.shuffle!
>    end
>
> end
>
> What I don't understand is the line "dup.shuffle!"
>
> What is the dup object?
>

dup returns a copy (duplicate) of the object. In the above code, it is
used to let you get back a shuffled copy of the Array, without
shuffling the original.

type:
ri Object#dup
for more info.