feature tnum {
    sub zero by zero.tnum;
    sub one by one.tnum;
    sub two by two.tnum;
    sub three by three.tnum;
    sub four by four.tnum;
    sub five by five.tnum;
    sub six by six.tnum;
    sub seven by seven.tnum;
    sub eight by eight.tnum;
    sub nine by nine.tnum;
} tnum;
