Abstraction of additive numeric types which support a unary operation -x producing the additive inverse of x. Every Invertible type supports a binary subtraction operation x-y.

Integer negativeOne = -1;
Float delta = x-y;

A concrete class that implements this interface should be a mathematical group. That is, it should have an additive identity, denoted 0, and satisfy:

• 0+x == x+0 == x
• x + -x == 0

Subtraction must be defined so that it is consistent with the additive inverse:

• x - y == x + -y