def print { stdout fprint }
def println { stdout fprint "\n" stdout fprint }
def nl { "\n" stdout fprint }

def eprint { stderr fprint }
def eprintln { stderr fprint "\n" stderr fprint }

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

def dip { swap [] curry compose call }
def 2dip { swap [dip] dip }
def 3dip { swap [2dip] 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];
}