パイプっていいます

pipe.rb

## PIPE BY PAIP ON MATZ LISP
## 2014-12-23
# (primes 10)
# => [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]

def make_pipe(head, tail)
  [head, tail]
end

def head(pipe)
  pipe[0]
end

def tail(pipe)
  if pipe[1].kind_of?(Proc)
    pipe[1] = pipe[1].()
  else
    pipe[1]
  end
end

def butlast(ary)
  ary[0..-2]
end

def pipe_to_array(pipe)
  butlast pipe.flatten
end

def iterate(f, x)
  [x, -> { iterate f, f.(x) }]
end

def take(count, pipe)
  if pipe.nil? or count == 0
    nil
  else
    [head(pipe), take(count - 1, tail(pipe))]
  end
end

def filter(f, pipe)
  if f.(head(pipe))
    [head(pipe), -> { filter f, tail(pipe) }]
  else
    filter(f, tail(pipe))
  end
end

def primes(n)
  sieve = ->(pipe){
    [
     head(pipe),
     -> {
       sieve.(filter(-> x { x % head(pipe) != 0 },
                     tail(pipe)))
     }
    ]
  }
  pipe_to_array take(n, sieve.(iterate(:succ.to_proc, 2)))
end

def nats(n = 1)
  [n, -> { nats(n + 1) }]
end

p primes 10
# => [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]

p pipe_to_array(take(10, nats))
# => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]