def print { file/stdout file/write }
def println { print "\n" print }

def when { [] if }
def unless { swap when }

def 2dip { swap [dip] dip }

def keep { over [call] dip }
def 2keep { [2dup] dip 2dip }

def bi { [keep] dip call }
def tri { [[keep] dip keep] dip call }

def times {
  if: over 0 =
    [drop drop]
    [swap over >r >r call r> 1 - r> times];
}

def while {
  swap dup bury >r >r
  if: call dup
    [r> dup >r call r> r> swap while]
    [drop r> drop r> drop];
}