Chapter 12

Exercise: ControlFlow-1

defmodule FizzBuzz do
  def upto(n) when n > 0, do: 1..n |> Enum.map(&fizzword/1)

  defp fizzword(n) do
    case {n, rem(n, 3), rem(n, 5)} do
      {_, 0, 0} -> "FizzBuzz"
      {_, 0, _} -> "Fizz"
      {_, _, 0} -> "Buzz"
      _ -> n
    end
  end
end

FizzBuzz.upto(20)

Exercise: ControlFlow-2

In general, using separate functions with guard clauses is the best option, but in this case the case style is good enough I think. Probably because this is very easy to implement, and it seems to be readable that expressions for the remainder and its conditionals are close. It is easy to remind the order and meaning of the three numbers.

“Don’t Control, Guard.”

Exercise: ControlFlow-3

ok! = fn
  {:ok, data} -> data
  {_, error} -> raise "Error: #{error}"
end

ok!.(File.open("somefile"))