a 'Monus' is a commutative monoid that allows a notion of substraction.

A Monus is a commutative monoid that allows a notion of substraction, with the following laws:

x <> (y - x) = y <> (x - y)

(x - y) - z = x - (y <> z)

x - x = mempty

mempty - x = mempty

monus

A 'Monus' is a commutative monoid that allows a notion of substraction, with the following laws:

• x <> (y - x) = y <> (x - y)
• (x - y) - z = x - (y <> z)
• x - x = mempty
• mempty - x = mempty

You can read more about them here: https://en.wikipedia.org/wiki/Monus

Installation

Install with cabal-install.