From: William James <w_a_x_man@...>
Date: 2007-02-03T10:35:10+09:00
Subject: Re: cartesian product of arrays

On Feb 2, 4:04 pm, Thomas Hafner <tho...@hafner.NL.EU.ORG> wrote:
> "William James" <w_a_x_...@yahoo.com> wrote/schrieb <1170361559.491476.96...@p10g2000cwp.googlegroups.com>:
>
> > Here's a shorter but slower way.
>
> > def cart_prod( *args )
> >   args.inject([[]]){|old,lst|
> >     lst.inject([]){|new,e|
> >       new + old.map{|c| c.dup << e}}}
> > end
>
> Wow, it's really short. Maybe it's not slower at all. Did you just
> that? Or did you compare it actually?
>
> Regards
>   Thomas


I tested it; it's slower.  This one isn't quite as slow.

def cart_prod( *args )
  args.inject([[]]){|old,lst|
    new = []
    lst.each{|e| new += old.map{|c| c.dup << e }}
    new
  }
end