Custom Enum With Reduce

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Custom Enum With Reduce

You’re going to use Enum.reduce/2 and/or Enum.reduce/3 to re-implement several of the Enum module’s functions. Only implement these functions for lists.

Example Solution ```elixir defmodule CustomEnum do def reverse(list) do Enum.reduce(list, [], fn each, acc -> [each | acc] end) end def map(list, callback_function) do Enum.reduce(list, [], fn each, acc -> [callback_function.(each) | acc] end) |> Enum.reverse() end def filter(list, callback_function) do Enum.reduce(list, [], fn each, acc -> if callback_function.(each) do [each | acc] else acc end end) |> Enum.reverse() end def sum(list) do Enum.reduce(list, 0, fn each, acc -> acc + each end) end def join(list_of_strings) do Enum.reduce(list_of_strings, "", fn str, acc -> acc <> str end) end end ```

Implement the CustomEnum module according to the documentation below.

defmodule CustomEnum do
  @moduledoc """
  Documentation for `CustomEnum`.
  Re-implement common [Enum](https://hexdocs.pm/elixir/Enum.html) functions using [Enum.reduce/2](https://hexdocs.pm/elixir/Enum.html#reduce/2) or [Enum.reduce/3](https://hexdocs.pm/elixir/Enum.html#reduce/3).
  """

  @doc """
  Reverse a list

  ## Examples

    iex> CustomEnum.reverse([1, 2, 3])
    [3, 2, 1]

    iex> CustomEnum.reverse([4, 5, 6, 7])
    [7, 6, 5, 4]
  """
  def reverse(list) do
  end

  @doc """
  Map over a list

  ## Examples

    iex> CustomEnum.map([1, 2, 3], fn integer -> integer * 2 end)
    [2, 4, 6]

    iex> CustomEnum.map([5, 4, 3], fn integer -> is_integer(integer) end)
    [true, true, true]
  """
  def map(list, callback_function) do
  end

  @doc """
  Filter elements in a list. Keep elements that return `true` when called with the
  provided callback function.

  ## Examples

    iex> CustomEnum.filter([1, 2, "3"], fn int -> is_integer(int) end)
    [1, 2]

    iex> CustomEnum.filter([1, "2", "3"], fn char -> is_bitstring(char) end)
    ["2", "3"]
  """
  def filter(list, callback_function) do
  end

  @doc """
  Sum a list of integers.

  ## Examples

    iex> CustomEnum.sum([1, 2, 3])
    6

    iex> CustomEnum.sum([1, 1, 1])
    3
  """
  def sum(list_of_integers) do
  end

  @doc """
  Join a list of strings together.

  ## Examples

    iex> CustomEnum.join(["A", "B", "C"])
    "ABC"

    iex> CustomEnum.join(["Hello", ",", " ", "World", "!"])
    "Hello, World!"
  """
  def join(list_of_strings) do
  end
end

Commit Your Progress

DockYard Academy now recommends you use the latest Release rather than forking or cloning our repository.

Run git status to ensure there are no undesirable changes. Then run the following in your command line from the curriculum folder to commit your progress.

$ git add .
$ git commit -m "finish Custom Enum With Reduce exercise"
$ git push

We’re proud to offer our open-source curriculum free of charge for anyone to learn from at their own pace.

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