Re: iterating over sub arrays

On Sunday, May 16, 2010 05:19:05 pm James Harrison wrote:
> <-----code----->
> array1 = ["0", "1", "2", "3"]
> array2 = ["jam", "bees", "please"]
> array3 = ["6", "7", "8"]
> 
> array1.each do |a|
>   array2.each do |b|
>     array3.each do |c|
>       puts "#{a} #{b} #{c}"
>     end
>   end
> end
> <-----/code----->
> 
> The output of that little snippet is all of the possible iterations of the
> three arrays.
> 
> I want to generalise this, such that if I have an arbitrary length array of
> arrays:
> 
> arrayCollection = [["0", "1", "2", "3"], ["jam", "bees", "please"], ["6",
> "7", "8"]]

Minor nit: by convention, Ruby people tend to use CamelCase for constants 
only, and underscores for variables. Call it array_collection.

Anyway, seems like one obvious way would be recursion:

def each_join array, context=[], &block
  if array.length == 0
    yield context
  else
    first = array.first
    rest = array[1...array.length]
    first.each do |elem|
      each_join rest, context+[elem], &block
    end
  end
end

Not pretty, and I'm sure someone could improve it, but it works.

It does seem pretty weird, though. Out of curiosity, what do you need this 
for?