From: Ben Tilly <ben_tilly@...>
Date: 2000-12-18T09:51:29+09:00
Subject: [ruby-talk:7526] Re: flatten_by(n)

David Alan Black <dblack@candle.superlink.net> wrote:
>
>On Mon, 18 Dec 2000, David Alan Black wrote:
>
> > On Mon, 18 Dec 2000, David Alan Black wrote:
> >
> > Next iteration:
> >
> >   def flatten_once
> >     res = []
> >     for e in self
> >       res.push e if e.nil?
> >       res += e.to_a
> >     end
> >     res
> >   end
> >
>
>I don't know about the rest of you, but I've learned a lot today about
>how arrays get extended in Ruby :-)

:-)

>The above breaks on empty strings.  "".to_a => [], and
>[1,2,3] + [] == [1,2,3].  So if you have "" in the original
>array, it will disappear.

Strings turn into arrays of characters?  I think I
understand why but I still don't really like that.

>So -- I'm actually back to something quite similar to Ben's
>first suggestion, in response to my recursive version, except
>I'm using concat instead of '+=' because concat is a lot faster.
>(Surprisingly faster, to me.)

It it surprising to me that it is faster.  IMO += should be just
syntactic sugar...

>   def flatten_once
>     res = []
>     for e in self
>       if e.is_a? Array then res.concat e else res.push e end
>     end
>     res
>   end
>
>
>For the record:
>
>30000 iterations:
>
>       user     system      total        real
>  10.330000   0.000000  10.330000 ( 10.327764)  # res.concat ...
>  13.490000   0.000000  13.490000 ( 13.506367)  # res += ...
>
>And now I really must go do some real work....

I didn't contribute much, but it was fun watching. :-)

Cheers,
Ben
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