Interface GroupExceptZero<G>

A structure of 2-term operation combine and 1-term operation invert, which must satisfy following conditions except zero element:

• Associative: for all x, y and z; combine(combine(x, y), z) equals to combine(x, combine(y, z)).
• Identity: for all x; combine(x, identity) equals to combine(identity, x) and x.
• Inverse: for all x; combine(x, invert(x)) equals to combine(invert(x), x) and identity.