Determining if a number is odd or even

Determining if a number is odd or even

sub is_even (Int $val) returns Bool { ($val <= 0) ?? 1 :: is_odd($val - 1)  }
sub is_odd  (Int $val) returns Bool { ($val <= 0) ?? 0 :: is_even($val - 1) }

say "... mutually recursive even and odd predicates";
say is_even(4);
say is_odd(4);
say is_even(5);
say is_odd(5);

sub is_even { not (shift % 2) }
sub is_odd  { not is_even }