Instance CompSpecs : compspecs.Definition Vprog : varspecs.Definition putchar_spec := DECLARE _putchar putchar_spec.Definition getchar_spec := DECLARE _getchar getchar_spec.Definition chars_of_Z z := chars_of_nat (Z.to_nat z).Definition ext_link := ext_link_prog prog.Instance IO_Espec : OracleKind := Build_OracleKind _ (IO_ext_spec ext_link).

Lemma chars_of_nat_intr : forall n, (0 < n)%nat -> chars_of_nat n = intr n.