Definition dest_below (dst: destination) (g: generator) : Prop :=
match dst with
| For_set sd => Plt (sd_temp sd) g.(gen_next)
| _ => True
end.
Remark dest_for_val_below: forall g, dest_below For_val g.

Lemma dest_below_le:
forall dst g1 g2,
dest_below dst g1 -> Ple g1.(gen_next) g2.(gen_next) -> dest_below dst g2.