Class Exp_not_FTZ :=
  exp_not_FTZ : forall e, (fexp (fexp e + 1) <= fexp e)%Z.Class Exp_not_FTZ :=
  exp_not_FTZ : forall e, (fexp (fexp e + 1) <= fexp e)%Z.

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