From: Dave Burt <dave@...>
Date: 2005-08-08T08:01:08+09:00
Subject: Re: cartesian product

walter a kehowski...
>    c=[]
>    each {|ae| b.each {|be| c << [ae, be] } }
>    c.collect! {|ce| ce.flatten}

Flatten is going to squash nested arrays. Maybe:

inject([]) {|c, ae| c.concat b.map {|be| [ae, be] } }

>
> c=a[0]
> as=a.slice(1..a.length-1)

You can do this (in Perl, too):
  as = a.slice(1..-1)
or this:
  as = a[1..-1]

> as.each {|ase| c=c.cartprod(ase) }
> c.each  {|ce| ce.each {|x| print x," " }; print "\n" }
>
> Would the following be desirable? If cartprod has two or more arguments, 
> do the usual thing, but if it has just one, it takes the cartesian product 
> with that argument, i.e, cartprod(a) gives cartprod(a,a) or a.cartprod(a), 
> etc.

I wouldn't. Typing an extra argument makes the function clearer - cartesian 
product is a two-array function.

> And thanks for all the suggestion so far. I usually just play around with 
> Perl but got $#@% fatigue. It was a toss-up between Python and Ruby so 
> here I am.

You're welcome.

Cheers,
Dave