From: Kristof Bastiaensen <kristof@...>
Date: 2004-05-17T20:34:05+09:00
Subject: RCR: More enumerator functionality

Hi,
I would like to know your opinion about the following idea's.
(It is actually are two RCR's)

(1)* Enumerable::filter and Enumerable::enum_filter

filter([[method = :each], *args, ] block)
  yield values for which block returns true

3.filter(:times, &lambda{ |i| i[0] == 0 }) do |n|
  puts "%i is even" % n
end
=> 2 is even

composers = %W(Brahms Berlioz Chopin)
composers.filter(&lambda { |i| i[0] == ?B }) do |c|
  puts "composer with B: #{c}"
end
=>  composer with B: Brahms
=>  composer with B: Berlioz

and now the fun stuff (turning into an enum):

5.enum_filter(:times){ |i| i[0] == 0 }.collect
=> [2, 4]

(2)* Enumerable::Enumerator takes a optional block

powers = 4.enum_for(:times){ |i| i * i  }
powers.collect 
=> [0, 1, 4, 9]

Thanks,
Kristof