What is the recommended data type for handling Money (just 2-decimal places) in Elixir/Erlang?

Question

What is the recommended data type for handling Money - numeric values with just 2-decimal places in Elixir/Erlang?

Answer 1

I think you should always use integers when handling money. Floating point operations can have rounding errors and money-handling code that's off even by 1 cent is often not ok. For example, instead of

amount = 99.99

Use

amount_cents = 9999

This is doubly important if you are storing the amount in a database since conversion between Elixir and your database and back may produce undesirable results.

Answer 2

I highly recommend using the Decimal library. There has been a lot of thought and work put into handling all the difficult edge cases.

Money, like cryptography, is not something you should implement yourself. You will get it wrong.

Answer 3

Using the Decimal library is the way to go in currency handling logic, especially when you have to perform arithmetic operations with the quantities.