fact: Record mixin_of (T : Type) := Mixin { mx_leq : T -> T -> Prop; _ : forall x, mx_leq x x; _ : forall x y, mx_leq x y -> mx_leq y x -> x = y; _ : forall x y z, mx_leq x y -> mx_leq y z -> mx_leq x z}.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun)