Section Fprop_Sterbenz.
Variable beta : radix.
Notation bpow e := (bpow beta e).
Variable fexp : Z -> Z.
Context { valid_exp : Valid_exp fexp }.
Context { monotone_exp : Monotone_exp fexp }.
Notation format := (generic_format beta fexp).

Theorem generic_format_plus :
forall x y,
format x -> format y ->
(Rabs (x + y) <= bpow (Z.min (mag beta x) (mag beta y)))%R ->
format (x + y)%R.