This page concerns the + operator on numbers; for the + operator on types, see sum types; for the + operator on graphs, see overlay.

Values of all numeric types can be added using the + operator. For example:

Disco> 1 + 2
Disco> (-5) + 2/3

If you ask for the type of +, you get

Disco> :type +
~+~ : ℕ × ℕ → ℕ

which says that it is a function taking a pair of natural numbers and returning a natural number. However, as mentioned above, it also works on other numeric types such as integers and rational numbers.