REM �A�֐� F(x,y)=0
LET a=1.00000001
DEF F(x,y)=x^3+y^3-3*x*y
SET WINDOW -2,2,-2,2
DRAW axes
SET POINT style 1
LET h=0.005
FOR x=-3 TO 3-h STEP h
   FOR y=-3 TO 3-h STEP h
      IF F(x,y)=0 THEN
         PLOT POINTS:x,y
      ELSEIF F(x,y)*F(x,y+h)<0 THEN
         PLOT POINTS:x,y+h/2
      END IF
       
   NEXT y
NEXT x
FOR y=-3 TO 3-h STEP h
   FOR x=-3 TO 3-h STEP h
      IF F(x,y)=0 THEN
         PLOT POINTS:x,y
      ELSEIF F(x,y)*F(x+h,y)<0 then
         PLOT POINTS:x+h/2,y
      END IF
   NEXT x
NEXT y
END