func addmod(a, b, m: StInt): StInt {....raises: [], noinit, ...gcsafe.}
func mulmod(a, b, m: StInt): StInt {....raises: [], noinit, ...gcsafe.}
func powmod(base, exp, m: StInt): StInt {....raises: [ValueError], raises: [], noinit, ...gcsafe.}
func submod(a, b, m: StInt): StInt {....raises: [], noinit, ...gcsafe.}