From: Robert Klemme <bob.news@...>
Date: 2006-03-28T19:23:55+09:00
Subject: Re: Noob: The ruby way to multiple Array by multiple?

Eric Luo wrote:
> I want to make a Array multipled by another Array, and the following semantic.
> For example:
>  [1, 2, 3] * [4, 5]
> then I will want [[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]] returned.
> 
> I have the following code snippet to implement this function:
> 
> class Array
>   alias_method :orig_multiple, :*
>   def *(arg)
>     case arg
>     when Array
>       if arg.empty?
>         self
>       else
>         inject([]) do |product, item|
>           product.concat(arg.collect do |i|
>                            case item
>                            when Array
>                              item.clone << i
>                            else
>                              [item, i]
>                            end
>                          end)
>         end
>       end
>     else 
>       orig_multiple(arg)
>     end
>   end
> end
> 
> It works but seems ugly.
> 
> Could anyone please to give me a clue to make it beauty and rubish!
> 
> Thx in advance.
> Eric

res = []
a1.each {|e1| a2.each {|e2| res << [e1,e2]}}

Or, if you prefer inject

a1.inject([]) {|arr,e1| a2.each {|e2| arr << [e1,e2]}; arr }

Kind regards

	robert