(
  (globals . (
    (mac . [(def mac (litmac litfn () (name params . body)
  `(def ,name (litmac litfn () ,params ,@body))))])
    (when . [(mac when (cond body)
  `(if ,cond ,body ()))])
    (let . [(mac let (var val . body)
  `((fn (,var) ,@body) ,val))])
    (hline . [(def hline (fn (screen y color)
  (hline1 screen y 0 (width screen) color)))])
    (hline1 . [(def hline1 (fn (screen y x xmax color)
  (while (< x xmax)
    (pixel screen x y color)
    (set x (+ x 1)))))])
    (vline . [(def vline (fn (screen x color)
  (vline1 screen x 0 (height screen) color)))])
    (vline1 . [(def vline1 (fn (screen x y ymax color)
  (while (< y ymax)
    (pixel screen x y color)
    (set y (+ y 1)))))])
    (fill_rect . [(def fill_rect (fn (screen x1 y1 x2 y2 color)
  (while (< y1 y2)
    (hline1 screen y1 x1 x2 color)
    (set y1 (+ y1 1)))))])
  (brline . [(def brline (fn (screen x0 y0 x1 y1 color)
  (let (x y) `(,x0 ,y0)
  (let dx (abs (- x1 x0))
  (let dy (- 0 (abs (- y1 y0)))
  (let sx (sgn (- x1 x0))
  (let sy (sgn (- y1 y0))
  (let err (+ dx dy)
  (while (not (and (= x x1)
                   (= y y1)))
    (pixel screen x y color)
    (let e2 (* err 2)
    (when (>= e2 dy)
      (set x (+ x sx)))
    (when (<= e2 dx)
      (set y (+ y sy)))
    (set err
      (+ err
         (+ (if (>= e2 dy)
              dy
              0)
            (if (<= e2 dx)
              dx
              0))))))))))))))])
  (read_line . [(def read_line (fn (keyboard)
  (let str (stream)
  (let c (key keyboard)
    (while (not (or (= c 0) (= c 10)))
      (write str c)
      (set c (key keyboard))))
  str)))])
  (chessboard . [(def chessboard (fn (screen px)
  (chessboard1 screen px 0 15)))])
  (chessboard1 . [(def chessboard1 (fn (screen px y color)
  (clear screen)
  (while (< y (height screen))
    (chessboard2 screen px y 0 color)
    (set y (+ y px))
    (chessboard2 screen px y px color)
    (set y (+ y px)))))])
  (chessboard2 . [(def chessboard2 (fn (screen px y x color)
  (while (< x (width screen))
    (fill_rect screen x y (+ x px) (+ y px) color)
    (set x (+ x px))
    (set x (+ x px)))))])
  (brcircle . [(def brcircle (fn (screen cx cy r color)
  ((fn (x y err continue)
     (while continue
       (pixel screen (- cx x) (+ cy y) color)
       (pixel screen (- cx y) (- cy x) color)
       (pixel screen (+ cx x) (- cy y) color)
       (pixel screen (+ cx y) (+ cy x) color)
       (set r err)
       (if (<= r y)
         (set err (+ err (+ 1 (* 2 (set y (+ y 1))))))
         ())
       (if (or (> r x) (> err y))
         (set err (+ err (+ 1 (* 2 (set x (+ x 1))))))
         ())
       (set continue (< x 0))
       ))
    (- 0 r)
    0
    (- 2 (* 2 r))
    1
   )))])
  (main . [(def main (fn (screen keyboard)
  (chessboard screen 16)))])
  ))
  (sandbox . (brline screen 1 1 5 5 4))
)