intros p q; case p; case q; simpl in |- *; intros;
apply (f_equal2 (A1:=Z) (A2:=Z)); auto.
Qed.

Theorem floatDec : forall x y : float, {x = y} + {x <> y}.
intros x y; case x; case y; intros Fnum2 Fexp2 Fnum1 Fexp1.