Leap in Kitten

leap.ktn

// The exercism "Leap" program in Kitten
// http://exercism.io/exercises/ruby/leap/readme
// http://kittenlang.org/

1996 isLeapYear "1996 is a leap year" assert
1997 isLeapYear "1997 is not a leap year" refute
1998 isLeapYear "1998 is not a leap year" refute
1900 isLeapYear "1900 is not a leap year" refute
1800 isLeapYear "1800 is not a leap year" refute
2400 isLeapYear "2400 is a leap year" assert
2000 isLeapYear "2000 is a leap year" assert

define isLeapYear (int -> bool):
  -> x;
  x isQuadrennial && (x isCentennial) not || x isQuadricentennial

define isQuadrennial      (int -> bool): 4 isDivisibleBy
define isCentennial       (int -> bool): 100 isDivisibleBy
define isQuadricentennial (int -> bool): 400 isDivisibleBy

define isDivisibleBy (int int -> bool): (%) 0 (=)

define assert (bool [char] ->):
  -> got message;
  if ( got not ):
    message say

define refute (bool [char] ->):
  swap not swap assert