Ring
Definition: A ring is a set R with operation addition and multiplication such that:
- (R,+) is an Abelian (the identity elements for + is written as 0)
- (R,.) is associative, perhaps not commutative, without identity and without inverse.
- " . distributes over + " : r(r' + r") = rr' + rr" & (r' + r")r = r'r + r"r
