Forum: Ruby-core [Bug #3525] Enumerable#flat_map does not return a flatted enumerable

Bug #3525: Enumerable#flat_map does not return a flatted enumerable
http://redmine.ruby-lang.org/issues/show/3525

Author: Jan Lelis
Status: Open, Priority: Normal
Target version: 1.9.2
ruby -v: ruby 1.9.2dev (2010-07-02 revision 28524) [i686-linux]

Hi,

the new flat_map method does not return flatted enumerables:

irb(main):072:0> [[1,2],2,3].flat_map{|e|e}
=> [1, 2, 2, 3]
irb(main):071:0> [[1,2],2,3].flat_map.to_a
=> [[1, 2], 2, 3]

Issue #3525 has been updated by Yusuke Endoh.

Status changed from Open to Rejected

Hi,

2010/7/3 Jan Lelis <redmine@ruby-lang.org>:
> the new flat_map method does not return flatted enumerables:
>
> irb(main):072:0> [[1,2],2,3].flat_map{|e|e}
> => [1, 2, 2, 3]
> irb(main):071:0> [[1,2],2,3].flat_map.to_a
> => [[1, 2], 2, 3]

It is indeed confusing a little, but not a bug.

Enumerable#flat_map aggregates values that is returned from block call,
and returns a flattend array of these values.

Enumerator#to_a aggregates arguments that is passed to (implicit) block
and just returns it as an array.

Look and consider the result of [[1,2],2,3].reject.to_a.

--
Yusuke Endoh <mame@tsg.ne.jp>
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http://redmine.ruby-lang.org/issues/show/3525