Types for working with integers modulo some constant.

Mod and its synonym / let you wrap arbitrary numeric types in a modulus. To work with integers (mod 7) backed by Integer, you could use one of the following equivalent types:

Mod Integer 7
Integer `Mod` 7
Integer/7
ℤ/7

('ℤ' is a synonym for Integer provided by this library. In Emacs, you can use the TeX input mode to type it with \Bbb{Z}.)

The usual numeric typeclasses are defined for these types. You can always extract the underlying value with unMod.

Here is a quick example:

>>> 10 * 11 :: ℤ/7
5

It also works correctly with negative numeric literals:

>>> (-10) * 11 :: ℤ/7
2

Modular division is an inverse of modular multiplication. It is defined when divisor is coprime to modulus:

>>> 7 `div` 3 :: ℤ/16
13
>>> 3 * 13 :: ℤ/16
7

To use type level numeric literals you need to enable the DataKinds extension and to use infix syntax for Mod or the / synonym, you need TypeOperators.

To use type level numeric literals you need to enable the DataKinds extension:

>>> :set -XDataKinds

To use infix syntax for Mod or the / synonym, enable TypeOperators:

>>> :set -XTypeOperators