フィボナッチ数列 (Ruby の勉強)

fib.rb

fibonacci = Enumerator.new do |y|
  i = [0, 1]
  loop do
    y << i[0]
    i = [i[1], i[0] + i[1]]
  end
end

# 遅延評価
p fibonacci.lazy.map{|x| x ** 2}.take(20).force

fibonacci.rb

def f(a0, a1)
  Enumerator.new do |y|
    a = [a0, a1]
    loop {
      y << a[0]
      a = [a[1], yield(a[0], a[1])]
    }
  end
end

p f(0, 1){|a, b| a + b}.take(20)