ostream& operator<< (ostream& o, Point& p)  Nonmember function 
Used in Path::output() for writing
the x and y values of the projective_coordinates of Points to
out_stream . See Path Reference; Outputting.
This is a lowlevel function that ordinary users should never have to
invoke directly.

void output (void)  Function 
Writes the MetaPost code for drawing or undrawing a Point to
out_stream . Called by Picture::output() , when a
Shape on the Picture is a Point .
See Picture Reference; Outputting.

void suppress_output (void)  Virtual function 
Sets do_output to false , which causes a Point
not to be output. This function is called in
Picture::output() , when a Point cannot be projected.
See Picture Reference; Outputting.

virtual void unsuppress_output (void)  Virtual function 
Resets do_output to true , so that a Point can
potentially be output, if Picture::output() is called again for
the Picture the Point is on.
This function is called in
Picture::output() .
See Picture Reference; Outputting.

vector<shape*> extract (const Focus& f, const unsigned short proj, real factor)

Function 
Attempts to project the Point
using the arguments passed to Picture::output() , which calls this
function. If extract() succeeds,
it returns a vector<shape*> containing only the Point .
Otherwise, it returns an empty vector<shape*> .

bool set_extremes (void)  Virtual function 
Sets "extreme" values
for x, y, and z in projective_coordinates . This
is, of course, trivial for
Points , because they only have one x, y and zcoordinate.
So the maxima and minima for each coordinate are always the same.

valarray <real> get_extremes (void)

Virtual inline const function 
Returns projective_extremes .

real get_minimum_z (void)  Virtual const function 
real get_maximum_z (void)  Virtual const function 
real get_mean_z (void)  Virtual const function 
These functions return the minimum, maximum, and mean zvalue of the
Point .
get_minimum_z() returns projective_extremes[4] ,
get_maximum_z() returns projective_extremes[5] , and
get_mean_z() returns
(projective_extremes[4] + projective_extremes[5]) / 2 .
However, since a Point has only one zcoordinate
(from world_coordinates ), these values will all be the same.
These functions are pure virtual functions in 