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#### 2.2.7 Arcs

Arc `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 stroke settings.

Function: arc? object

  Returns ‘`#t`’ if and only if object is an arc `object`.

Function: make-arc center radius start-angle sweep-angle [color]

  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 sweep-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.

Function: set-arc! arc center radius start-angle sweep-angle [color]

  Sets the parameters of arc. The arguments are the same as to `make-arc`. Returns arc.

Function: arc-info arc

  Returns the parameters of arc as a list of the form:

      ((center-x . center-y) radius start-angle sweep-angle color)

Function: arc-center arc

  Returns the position of the center of arc in the form `(x . y)`.

Function: arc-radius arc

  Returns the radius of arc as an integer.

Function: arc-start-angle arc

  Returns the start angle of arc as an integer number of degrees.

Function: arc-sweep-angle arc

  Returns the end angle of arc as an integer number of degrees.

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