Name:    Implicit function sketcher
Models:  fx-4000P and above
Size:    122 bytes
Version: 1.0
Author:  Lupus Yonderboy
E-mail:  lupusy@afrodita.rcub.bg.ac.yu
URL:     http://www.rcub.bg.ac.yu/~lupusy/

Description:
   This  program  will  try  to plot function given in the implicit form,
   f(x,y).   Program  is  called sketcher, not plotter, becouse it really
   only  sketches  function.   Graphs  can be very rough and usually will
   need  a  lot  of time to plot, like 1-3 minutes, depending on the step
   value.

Usage:
   -X,  X,  -Y, and Y define area in which function will be ploted (Xmin,
   Xmax,  Ymin  and Ymax), Scale (J variable) is scale used in coordinate
   system,  and  Step  (E)  is  how  accurate program will try to be when
   plotting.   Optimal step value veries depending on function given, and
   is  between  0.1  (circles  and  ellipses)  and  0.2 - 0.3 (parabolla,
   hyperbolla...)  or even 0.5 - 0.6 for very large plots ('large' in the
   terms  of  -X,  X,  -Y, Y range - larger range == more time needed for
   plotting).

   <FUNC>  is  the  name  of  your  program  that  holds function you are
   plotting.  Function is given in the form of, eg:

      X^2 + Y^2 - 4  (circle with the centre in 0,0 and half radius of 2)

Example:
   Lets draw example from the above:

      X^2 + Y^2 = 4

   Transfrorm  it  to  X^2  + Y^2 - 4 = 0 and store X^2 + Y^2 - 4 in your
   <FUNC>  program.   Now,  since you know that this is a circle, and can
   see its param's, use the range of -2.1, 2.1, -2,1, 2,1, and set E=0.1.
   Experiment a bit with the E value and you will get the idea...

   Now,  this  was easy, but how to know to what values to set range when
   func.   is not in such 'clean' form?  You will need to experiment some
   more :)