An object that draws the graph of a function, calculating the values on demand (so there is no loss of precision when zooming in for example.)
Relevant part of the header :
An example of a correct function in C to be given as a
reference to PHGraphFunc could be (from example 3) :
Note that when this function is called, flag is initialized
to 0, so if there is no control to do as to the domain of
the function, just ignore the flag.