Definition sub_correct' : ltac:(auto_for_auto sub_correct) := sub_correct.
Hint Resolve sub_correct' : eval.

Lemma compare0_correct n: forall m tn tm,
evaluates tn (value_of_N n) ->
evaluates tm (value_of_N m) ->
evaluates (compare0F (: tn, tm :))
(value_of_comp (N.compare n m)).