Currency Conversion

Mix.install([
  {:kino, github: "livebook-dev/kino", override: true},
  {:kino_lab, "~> 0.1.0-dev", github: "jonatanklosko/kino_lab"},
  {:vega_lite, "~> 0.1.4"},
  {:kino_vega_lite, "~> 0.1.1"},
  {:benchee, "~> 0.1"},
  {:ecto, "~> 3.7"},
  {:math, "~> 0.7.0"},
  {:faker, "~> 0.17.0"},
  {:utils, path: "#{__DIR__}/../utils"},
  {:tested_cell, git: "https://github.com/BrooklinJazz/tested_cell"}
])

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Currency Conversion

You are building an app which accepts payments. Originally, your app was built assuming it would only accept a single currency, however it expands to accept multiple currencies.

You are tasked with the assignment of converting one currency to another according to the following conversion rates.

• Canadian Dollar (:CAD): $1.00
• US Dollar (:US): $1.29
• European Euro (:EUR): $1.39

While not a perfect solution, you may round currency conversions using round/1.

For example, 500 :EUR would become 360 :CAD.

round(500 / 1.39)

Remember that currency should not be stored in a float, instead money will be stored in a Money struct.

> “If I had a dime for every time I’ve seen someone use FLOAT to store currency, I’d have $999.997634” – Bill Karwin

• Create a Money struct with :amount and :currency.
• Create a convert/2 function to convert a money struct from one currency to another.
• Create an add/2 function to add one money struct of the same currency to another.
• Create a subtract/2 function to subtract one money struct of the same currency to another.
• Create a multiply function to multiply one money struct by a number.

Examples

five_eur = Money.new(500, :EUR)
%Money{amount: 500, currency: :EUR}

Money.convert(five_eur, :CAD)
%Money{amount: 695, currency: :EUR}

ten_eur = Money.add(five_eur, five_eur)
%Money{amount: 10_00, currency: :EUR}

hundred_eur = Money.multiply(ten_eur, 10)
%Money{amount: 100_00, currency: :EUR}

ninety_nine_eur = Money.subtract(hundred_eur, ten_eur)
%Money{amount: 90, currency: :EUR}

Money.add(%Money{amount: 500, :EUR}, %Money{amount: 500, :CAD})
** (FunctionClauseError) no function clause matching in Money.add/2

Enter your solution below.

defmodule Money do
  defstruct []

  def new(amount, currency) do
  end

  def convert(money, currency) do
  end

  def add(money1, money2) do
  end

  def multiply(money1, money2) do
  end

  def subtract(money1, money2) do
  end
end

Utils.feedback(:money, Money)

This exercise is inspired by the Elixir Money library.

Commit Your Progress

Run the following in your command line from the project folder to track and save your progress in a Git commit.

$ git add .
$ git commit -m "finish currency conversion exercise"