Section not_FTZ.
Class Exp_not_FTZ :=
exp_not_FTZ : forall e, (fexp (fexp e + 1) <= fexp e)%Z.
Context { exp_not_FTZ_ : Exp_not_FTZ }.

Theorem subnormal_exponent :
forall e x,
(e <= fexp e)%Z ->
generic_format x ->
x = F2R (Float beta (Ztrunc (x * bpow (- fexp e))) (fexp e)).