From: Farrel Lifson <farrel.lifson@...>
Date: 2007-02-15T04:26:48+09:00
Subject: Re: Justification for Array#join behaviour?

On 14/02/07, Bertram Scharpf <lists@bertram-scharpf.de> wrote:
> Hi,
>
> Am Mittwoch, 14. Feb 2007, 16:52:00 +0900 schrieb Farrel Lifson:
> > What is the justification for [1,2,[3,4]].join(',') being '1,2,3,4'
> > instead of '1,2,34'? According to ruby-doc.org join "Returns a string
> > created by converting each element of the array to a string, separated
> > by sep.". Why should an element be recursively joined if it's also an
> > array?
>
> You would have to ask for the objects type:
>
>   class Array
>     def deep_join sep
>       map { |x|
>         case x
>           when Array then x.deep_join sep
>           else            x.to_s
>         end
>       }.join sep
>     end
>   end
>
> I don't look at this as a smart programming style actually.
>
> The object-oriented approach is to redefine `to_s'.
>
> Bertram
>
>
> --
> Bertram Scharpf
> Stuttgart, Deutschland/Germany
> http://www.bertram-scharpf.de
>
>

I did some experimentation  and it seems that the decision might not
be that half bad. Take for instance a deeply nested array
[1,2,[3,4[5,6]]]. Currently calling join produces "1,2,3,4,5,6".
Whereas if we used the non-recursive join we'd get "1,2,3456" which
actually looks a bit worse. I think it would be better if the
documentation was amended to reflect that nested arrays will be
flattened.

Farrel