Natural numbers

The type of natural numbers is written N, ℕ, Nat, or Natural (Disco always prints it as ℕ, but you can use any of these names when writing code). The natural numbers include the counting numbers 0, 1, 2, 3, 4, 5, …

Adding or multiplying two natural numbers yields another natural number:

Disco> :type 2 + 3
5 : ℕ
Disco> :type 2 * 3
6 : ℕ

Natural numbers cannot be directly subtracted or divided. However, N is a subtype of all the other numeric types, so using subtraction or division with natural numbers will cause them to be automatically converted into a different type like integers or rationals:

Disco> :type 2 - 3
2 - 3 : ℤ
Disco> :type 2 / 3
2 / 3 : 𝔽

Note that some mathematicians use the phrase “natural numbers” to mean the set of positive numbers 1, 2, 3, …, that is, they do not include zero. However, in the context of computer science, “natural numbers” almost always includes zero.