From: Intransition <transfire@...>
Date: 2010-04-08T15:01:24+09:00
Subject: Re: Is it possible, a fully general Enumerable#recursive ?



On Apr 7, 11:51 pm, David Masover <ni...@slaphack.com> wrote:
> On Wednesday 07 April 2010 04:49:15 pm Intransition wrote:
>
> > For the last couple of days I've been trying to write an Enumerable
> > method called #recursive. Rather than create a bunch of methods like
> > #recursive_each, #recursive_map, #recursive_sort, etc. I figured that
> > it should be possible to create a single #recursive method that
> > returned an Enumerator,
>
> Yes!
>
> > or barring that a Functor,
>
> What's a Functor in this context? We already have proc objects, which is
> traditionally what "functor" means...

Functor is defined as:

  class Functor
    private(*instance_methods.select { |m| m !~ /(^__|^binding$)/ })
    def initialize(&function)
      @function = function
    end
    def to_proc
      @function
    end
    def method_missing(op, *args, &blk)
      @function.call(op, *args, &blk)
    end
  end

#method_missing is what makes it different from a Proc.

> > This works for #each and #map but not #sort.
>
> #sort isn't a method of Enumerable, it's a method of Array.

It seems to be according to ri.

> > Can anyone think of a better solution?
>
> Probably, but I'm not sure what it would look like. What's your use case --
> how would I actually use this to, say, generate an infinite stream of
> fibbonacci numbers?

I don't think anyone can generate that seeing that it's infinite and
all ;-)

> I guess I don't really see why you'd define it in terms of an enumerable (in
> that case, you probably want inject).

Perhaps Array is the more appropriate place for it.