module Lazily

def associate(source_map, &block)
  labels = source_map.keys
  tagged_element_sources = source_map.map do |label, enumerable|
    enumerable.lazily.map do |value|
      key = block ? block.call(value) : value
      TaggedElement.new(key, value, label)
    end
  end
  tagged_elements = Lazily.merge(*tagged_element_sources) { |te| te.key }
  tagged_elements.chunk { |te| te.key }.map do |_, tagged_elements|
    association = {}
    labels.each { |label| association[label] = [] }
    tagged_elements.each do |te|
      association[te.label] << te.value
    end
    association
  end
end

def concat(*enumerables)
  Concatenator.new(enumerables)
end

def dequeue(queue)
  Dequeuer.new(queue)
end

def merge(*enumerables, &block)
  Merger.new(enumerables, &block)
end

def zip(*enumerables)
  Zipper.new(enumerables)
end