From: Caleb Clausen <vikkous@...>
Date: 2010-04-10T04:02:46+09:00
Subject: Re: Is it possible, a fully general Enumerable#recursive ?

On 4/9/10, Intransition <transfire@gmail.com> wrote:
>> 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.

This has got to be a bug. It should at least either flatten or not
flatten consistently.

> On a side note, I am not so sure that raising an error
> is best. Why not just assume that too non-comparable things are equal?

Maybe it would help you write a #visit that sorts properly, but in
general, I would expect that if I try to sort a collection containing
non-comparable objects it's because I made a mistake and put the wrong
thing into the collection somehow. So I want to see that error.