From: Yusuke ENDOH <mame@...>
Date: 2009-10-25T11:04:05+09:00
Subject: [ruby-core:26287] Re: New Enumerable#flat_map

Hi,

2009/10/25 Marc-Andre Lafortune <ruby-core-mailing-list@marc-andre.ca>:
> I noticed the new Enumerable#flat_map (aka collect_concat) and I was
> wondering what prompted the creation of this method.
>
> I'm probably missing something, but what is the difference between:
>    enum.collect_concat(&block)
> and
>    enum.map(&block).flatten(1)
> ?
>
> In what kind of circumstances is flat_map needed?


I guess the rationale:

- map+flatten(1) is a bit too long in spite of a frequent idiom.
- flat_map is shorter and plainer than map+flatten(1).
- flat_map does not create intermediate array.
- flat_map is provided in Scala (and Haskell).  [direct reason?]

http://twitter.com/yukihiro_matz/statuses/5108220843

Thanks,

-- 
Yusuke ENDOH <mame@tsg.ne.jp>