objects are specified by center position, radius, and start
and end angles. They are purely graphical with no electrical
meaning. They can be drawn in different colors, and with various
Creates and returns a new arc
object. center is the position of the center of the new arc in the form
(x . y), and radius is the integer radius of the arc. start-angle and end-angle are the angles at which to start and end the arc, in degrees. If color is specified, it should be the integer color map index of the color with which to draw the arc. If color is not specified, the default arc color is used.
Sets the parameters of arc. The arguments are the same as to
make-arc. Returns arc.
Returns the parameters of arc as a list of the form:((center-x . center-y) radius start-angle end-angle color)