From: Robert Dober <robert.dober@...>
Date: 2008-11-30T19:11:00+09:00
Subject: Re: Enumerable#select used to return actual values

On Sun, Nov 30, 2008 at 8:54 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 30.11.2008 04:46, Mike Austin wrote:
>>
>> I'm pretty sure select used to use the actual value of the called block,
>> instead of treating it as just a truthy/falsey boolean.
>
> I am pretty sure it did never.  Maybe you have a combination with to_enum in
> mind or rather inject?
>
>>  I know this is unconventional, but it's a really nice, compact way of
>> expressing map and filter in one shot, like list comprehension:
>>
>> (1..10).select { |a| a * a if a > 5 }
>>
>> Was it ever there, or did I just have a dream about it?  It's easy to
>> implement... just wondering.
>
> Maybe 1.9 has a nifty trick, I don't use it that often yet.
>
> As said, inject is always a good candidate for this:
>
> irb(main):005:0> (1..10).inject([]) {|r,a| r << (a*a) if a > 5; r}

As Robert was the first to suggest inject I am left with the less
attractive joices ;)


a.map{ |a| a > 5 ? a*a: nil}.compact # does not work for any &blk of course

or

myselection = proc{ |a| a*a if a > 5}
a.select(&myselection).map(&myselection)

or

module Enumerable
   def map_selection &blk
      select( &blk ).map( &blk )
   end
end

HTH
Robert
-- 
Ne baisse jamais la tête, tu ne verrais plus les étoiles.

Robert Dober ;)