paiza.ioでelixir その336

概要

paiza.ioでelixirやってみた。
Streamに、なじめないので、訓練してみた。

サンプルコード

#Stream.unfold(カウンタ初期値, fn カウンタ変数 -> {リストに出力される各要素, カウンタの次の値} end)

Stream.unfold(5, fn
    0 -> 
        nil
    n -> 
        {n, n - 1}
end)
|> Enum.take(10)
|> IO.inspect

Stream.unfold(0, fn
    x -> 
        {x + 1, x + 1}
end)
|> Enum.take(10)
|> IO.inspect

Stream.unfold(0, fn
    x -> 
        {x, x + 2}
end)
|> Enum.take(10)
|> IO.inspect



 f = fn list, default_value ->
        Stream.unfold(list, fn
            [] -> 
                {default_value, []}
            [h | t] -> 
                {h, t}
        end)
    end
s = f.([1, 2], 0)
Enum.take(s, 10)
|> IO.inspect

s = f.([9, 8, 7, 6, 5, 4, 3, 2, 1], 0)
Enum.take(s, 10)
|> IO.inspect

Stream.unfold(5, fn
    0 -> 
        nil
    n -> 
        {n, n - 1}
end) 
|> Enum.to_list()
|> IO.inspect



Enum.map(1..10_000, &(&1 + 1)) 
|> Enum.take(5)
|> IO.inspect

Stream.map(1..10_000, &(&1 + 1)) 
|> Enum.take(5)
|> IO.inspect


Stream.map([1, 2, 3], fn x -> 
    x * 2 
end)
|> Enum.to_list()
|> IO.inspect

Stream.cycle([1, 2, 3])
|> Enum.take(5)
|> IO.inspect

Stream.iterate(0, &(&1 + 1)) 
|> Enum.take(10)
|> IO.inspect


fib = Stream.iterate({1, 1}, &({ elem(&1, 1), elem(&1, 0) + elem(&1, 1)})) 
    |> Stream.map(&(elem(&1, 0)))
fib 
|> Enum.take(10)
|> IO.inspect

Stream.filter([1, 2, 3], fn x -> 
    rem(x, 2) == 0 
end)
|> Enum.to_list()
|> IO.inspect

concat = Stream.concat(1..3, 4..6)
cycle = Stream.cycle([:a, :b, :c])
Stream.zip(concat, cycle) 
|> Enum.to_list()
|> IO.inspect

defmodule FizzBuzz do
  def print(n) do
    generate2
    |> Stream.take(n)
    |> Stream.each(&IO.puts/1)
    |> Stream.run
  end
  def generate do
    fizzes = Stream.cycle(["Fizz", "", ""])
    buzzes = Stream.cycle(["Buzz", "", "", "", ""])
    Stream.zip(fizzes, buzzes)
    |> Stream.map(&concat/1)
    |> Stream.with_index
    |> Stream.map(&translate/1)
    |> Stream.drop(1)
  end
  def generate2 do
    fizzes  = Stream.cycle(["", "", "Fizz"])
    buzzes  = Stream.cycle(["", "", "", "", "Buzz"])
    indexes = Stream.iterate(1, &(&1 + 1))
    Stream.zip(fizzes, buzzes)
    |> Stream.map(&concat/1)
    |> Stream.zip(indexes)
    |> Stream.map(&translate/1)
  end
  defp concat({f, b}), do: f <> b
  defp translate({"",   n}), do: to_string(n)
  defp translate({str, _n}), do: str
end


FizzBuzz.print(15)

実行結果

[5, 4, 3, 2, 1]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
[1, 2, 0, 0, 0, 0, 0, 0, 0, 0]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
[5, 4, 3, 2, 1]
[2, 3, 4, 5, 6]
[2, 3, 4, 5, 6]
[2, 4, 6]
[1, 2, 3, 1, 2]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
[2]
[{1, :a}, {2, :b}, {3, :c}, {4, :a}, {5, :b}, {6, :c}]
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz

成果物

以上。