[ruby-core:18139] Re: Enumerators that know about a block

Hi,

2008/8/6 David A. Black <[e-mail]>:
>> You may need the lazy version of Enumerable#map that returns
>> Enumerator instead of Array.
>>
>>  e = [1, 2, 3].lazy_map {|x| x * 10}
>>  p e.next #=> 10
>>  p e.next #=> 20
>
> Is that an actual method (I couldn't find it anywhere) or just a
> hypothetical example? I'm still wondering why enumerators aren't
> designed to do that automatically if they're given a block upon
> initialization.

It's just a hypothetical example.  Enumerator can't do that automatically,
because Enumerable#map is implemented to produce Array.

If you don't mind memory consumption, you can write like this:

  e = [1, 2, 3].map {|x| x * 10}.each
  p e.next #=> 10
  p e.next #=> 20

-- 
Shugo Maeda