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
Returns ‘#t’ if and only if object is an arc
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)
Returns the position of the center of arc in the form
(x . y).
Returns the radius of arc as an integer.
Returns the start angle of arc as an integer number of degrees.
Returns the end angle of arc as an integer number of degrees.