Stack Underflow - Elixir - Exercism

exception.ex

defmodule RPNCalculator.Exception do
  defmodule DivisionByZeroError do
    defexception message: "division by zero occurred"
  end

  defmodule StackUnderflowError do
    defexception message: "stack underflow occurred"

    @impl true
    def exception(value) do
      case value do
        [] ->
          %StackUnderflowError{}

        _ ->
          %StackUnderflowError{message: "stack underflow occurred, context: " <> value}
      end
    end
  end

  def divide(stack) when length(stack) < 2, do: raise(StackUnderflowError, "when dividing")
  def divide([0, _nominator] = _stack), do: raise(DivisionByZeroError)
  def divide([divisor, nominator]) when divisor != 0, do: nominator / divisor
end