add type check guards to comparators
add type check guards to comparators

ktakashi/picrin,leavesbnw/picrin,leavesbnw/picrin,dcurrie/picrin,omasanori/picrin,ktakashi/picrin,omasanori/picrin,koba-e964/picrin,leavesbnw/picrin,ktakashi/picrin,koba-e964/picrin,picrin-scheme/picrin,picrin-scheme/picrin,koba-e964/picrin,dcurrie/picrin