Math With Guards

Mix.install([
  {:jason, "~> 1.4"},
  {:kino, "~> 0.9", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}
])

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Math

In this exercise, you’re going to use guards to create a Math module that handles adding and subtracting integers, strings, and lists. You do not need to handling adding or subtracting different data types.

Math.add(1, 2)
3

Math.add("Hello, ", "World!")
"Hello, World!"

Math.add([1, 2], [3, 4])
[1, 2, 3, 4]

Math.subtract(10, 2)
8

Math.subtract("hello there", "hello ")
"there"

Math.subtract([1, 2, 3, 4], [1, 3])
[2, 4]

Hint: Subtracting Strings

Consider converting your strings to a list, then subtract the two lists together then join your result back into a string.

Example Solution

defmodule Math do
  def add(integer1, integer2) when is_integer(integer1) and is_integer(integer2) do
    integer1 + integer2
  end

  def add(list1, list2) when is_list(list1) and is_list(list2) do
    list1 ++ list2
  end

  def add(string1, string2) when is_binary(string1) and is_binary(string2) do
    string1 <> string2
  end

  def subtract(integer1, integer2) when is_integer(integer1) and is_integer(integer2) do
    integer1 - integer2
  end

  def subtract(list1, list2) when is_list(list1) and is_list(list2) do
    list1 -- list2
  end

  def subtract(string1, string2) when is_binary(string1) and is_binary(string2) do
    String.split(string1, "")
    |> subtract(String.split(string2, ""))
    |> Enum.join()
  end
end

Implement the Math module as documented below.

defmodule Math do
  @moduledoc """
  Documentation for `Math`
  """

  @doc """
  Add two integers, strings, or lists.

  ## Examples

    iex> Math.add(2, 2)
    4
    iex> Math.add(4, 4)
    8

    Math.add([1, 2], [3, 4])
    [1, 2, 3, 4]
    Math.add([1, 2, 3], [4, 5, 6])
    [1, 2, 3, 4, 5, 6]

    iex> Math.add("abc", "def")
    "abcdef"
    iex> Math.add("123", "456")
    "123456"

    iex> Math.add(1.0, 2.0)
    ** (FunctionClauseError) no function clause matching in Math.add/2

    iex> Math.add(2, "2")
    ** (FunctionClauseError) no function clause matching in Math.add/2

    iex> Math.add({}, {})
    ** (FunctionClauseError) no function clause matching in Math.add/2

    iex> Math.add(%{}, %{})
    ** (FunctionClauseError) no function clause matching in Math.add/2
  """
  def add(value1, value2) do
  end

  @doc """
  Subtract two integers, strings, or lists.

  ## Examples

    iex> Math.subtract(10, 2)
    8
    iex> Math.subtract(20, 2)
    18

    iex> Math.subtract([1, 2], [1])
    [2]
    iex> Math.subtract([1, 2, 3, 4], [1, 3])
    [2, 4]

    iex> Math.subtract("abcd", "abc")
    "d"
    iex> Math.subtract("cbad", "abc")
    "d"
    iex> Math.subtract("abc", "xyz")
    "abc"
    iex> Math.subtract("abc", "xyza")
    "bc"

    iex> Math.subtract(1.0, 2.0)
    ** (FunctionClauseError) no function clause matching in Math.subtract/2

    iex> Math.subtract(2, "2")
    ** (FunctionClauseError) no function clause matching in Math.subtract/2

    iex> Math.subtract({}, {})
    ** (FunctionClauseError) no function clause matching in Math.subtract/2

    iex> Math.subtract(%{}, %{})
    ** (FunctionClauseError) no function clause matching in Math.subtract/2
  """
  def subtract(value1, value2) 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 Math With Guards exercise"
$ git push

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