From: Intransition <transfire@...>
Date: 2010-04-10T03:49:30+09:00
Subject: Re: Is it possible, a fully general Enumerable#recursive ?



On Apr 9, 11:01 am, Intransition <transf...@gmail.com> wrote:
> On Apr 7, 5:49 pm, Intransition <transf...@gmail.com> 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, or barring that a Functor, that would handle
> > any enumerable method, e.g. recursive.each, recursive.map,
> > recursive.sort, and so on. But I have yet to figure out fully general
> > solution.
>
> Working on this more I currently have the method #visit (see the code
> below). It almost works, but it has this one issue that makes no sense
> to me, and I wonder what is going on under the hood in Enumerator for
> it do this. It has the air of a bug to me --or at least a feature
> deficiency.
>
> Notice:
>
>   [1, 2, 3, ['a', 'b', 'c'] ].visit{ |x| x.succ }
>   => [2, 3, 4, ["b", "c", "d"]]
>
> But using Enumerator:
>
>   [1, 2, 3, ['a', 'b', 'c'] ].visit.map{ |x| x.succ }
>   => [2, 3, 4, "b", "c", "d"]
>
> Why is it flattening the result?

To just make that much stranger:

  [1, 2, 3, ['a', 'b', 'c'] ].visit.with_index{ |x,i| i }
  => [0, 1, 2, [3, 4, 5]]

Doesn't flatten, but somehow the index is being carried on to the
subarray iterations -- that really fracks with my mind.