Definition binop_float (sem: float -> float -> float) (x y: aval) :=
  match x, y with F n, F m => F (sem n m) | _, _ => ntop2 x y end.

Lemma binop_float_sound: forall sem v x w y, vmatch v x -> vmatch w y -> vmatch (match v, w with Vfloat i, Vfloat j => Vfloat(sem i j) | _, _ => Vundef end) (binop_float sem x y).