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Functional programming abstractions for Elixir (Beta release: APIs may change before 1.0)

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funx lib monoid product.ex
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lib/monoid/product.ex 

defmodule Funx.Monoid.Product do

  @moduledoc """

  A Monoid implementation for products.



  This monoid uses multiplication as its associative operation

  and `1` as the identity element.

  """



  @type t :: %__MODULE__{value: number()}



  defstruct value: 1

end



defimpl Funx.Monoid, for: Funx.Monoid.Product do

  alias Funx.Monoid.Product



  @spec empty(Product.t()) :: Product.t()

  def empty(_), do: %Product{}



  @spec append(Product.t(), Product.t()) :: Product.t()

  def append(%Product{value: a}, %Product{value: b}) do

    %Product{value: a * b}

  end



  @spec wrap(Product.t(), number()) :: Product.t()

  def wrap(%Product{}, value) when is_number(value), do: %Product{value: value}



  @spec unwrap(Product.t()) :: number()

  def unwrap(%Product{value: value}) when is_number(value), do: value

end