Fplus_compute@{} q r : (' q) + (' r) = ' (Frac.pl _ q r) := 1. Global Instance Fneg@{} : Negate F. Proof. refine (F_rec (fun x => ' (Frac.neg _ x)) _). intros;apply path; eapply Frac.neg_respect;try apply _. trivial. Defined.
Require Import HoTT.HIT.quotient. Require Import Import Frac.