04/05 1.25pm  CISC181 notes

Where the .h files live...

  /usr/include

For idempotent #include files, use:

#ifndef NAME_OF_FILE_H
#define NAME_OF_FILE_H

...


#endif

That way it only gets included once.


You may well wonder... who cares?  Why would I #include a file more than
once in the first place?


Consider:  


#include <iostream>
#include "drawings.h"



But inside drawings.h, I have a function prototype:


  void  drawCircle(ofstream &out, double radius, double x, double y);

That means that inside drawings.h, I need to have #include <iostream>

So, you would never want to #include a file more than once DIRECTLY,
but INDIRECTLY, it happens all the time!