new

Creates a new Lazy enumerator. When the enumerator is actually enumerated (e.g. by calling #force), obj will be enumerated and each value passed to the given block. The block can yield values back using yielder. For example, to create a method filter_map in both lazy and non-lazy fashions:

module Enumerable
  def filter_map(&block)
    map(&block).compact
  end
end

class Enumerator::Lazy
  def filter_map
    Lazy.new(self) do |yielder, *values|
      result = yield *values
      yielder << result if result
    end
  end
end

(1..Float::INFINITY).lazy.filter_map{|i| i*i if i.even?}.first(5)
    # => [4, 16, 36, 64, 100]