proposition: Fact opp_fun_is_additive : additive (\- g).
proof: Proof. by move=> x y /=; rewrite !raddfB opprB addrC opprK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)