Lazy streams

lazy_stream.rb

class A
  def initialize(*processors)
    @processors = processors
  end
  def call(list)
    @processors.inject(0) { |acc, p|
      acc + p.call(list)
    }
  end
end

class B
  def initialize(multiplier)
    @multiplier = multiplier
  end

  def call(list)
    list.map { |i|
      i * @multiplier
    }.inject(0) { |acc, i|
      puts "B with multipler: #{@multiplier}, adding: #{i}"
      acc + i
    }
  end
end

A.new(B.new(1), B.new(2)).call([1, 2, 3, 4, 5].lazy)
# => 45
# B with multipler: 1, adding: 1
# B with multipler: 1, adding: 2
# B with multipler: 1, adding: 3
# B with multipler: 1, adding: 4
# B with multipler: 1, adding: 5
# B with multipler: 2, adding: 2
# B with multipler: 2, adding: 4
# B with multipler: 2, adding: 6
# B with multipler: 2, adding: 8
# B with multipler: 2, adding: 10

# Desired output
# => 45
# B with multipler: 1, adding: 1
# B with multipler: 2, adding: 2
# B with multipler: 1, adding: 2
# B with multipler: 2, adding: 4
# B with multipler: 1, adding: 3
# B with multipler: 2, adding: 6
# B with multipler: 1, adding: 4
# B with multipler: 2, adding: 8
# B with multipler: 1, adding: 5
# B with multipler: 2, adding: 10