/* define valid mutually recursive functions */
let

function do_nothing1(a : int, b : string) : int=
                 (do_nothing2(a+1);0)

function do_nothing2(d : int) : string =
                 (if d < 10 then do_nothing1(d, "str") else 0;" ")

in
        do_nothing1(0, "str2")
end