gistfile1.txt

# in the right spirit of lazy evaluation & enumeration 

module Enumerable
  def  enum_block()
    Enumerator.new() {  |y|  each { |val|  yield(val, y) } }
  end
  
  def  lazy_select()
    Enumerator.new() { |y| each { |val| y << val if yield(val) } } 
  end
end

#  usage

def test_enum_block()
  a = (1..10).to_a
  la = a.lazy_select { |v| v.even? }

  # --------------------------------
  ba = a.enum_block { |v, y| y << v if v.odd? }
  
  # this one seems too trivial because of the trivial test
  # the right usage could be with havier resources with deeper nesting like calling from block 
  # e.g. 
  #     files.enum_block {  |fn, yld| TagLib::FileRef.open(fn) {  |fr|  yld  << fr if fr && fr.tag } }.each { |fr| puts fr.tag.track }
end

test_enum_block()