CMPT 212 Object-Oriented Applications Design in C++ Fall 1997

Comments in Header Files

• Function prototypes in header files should be commented with detailed descriptions about what the function does and about its parameters.
  • Everything that a programmer needs to know about using a function should be described here.

  • You should describe what a function does. How a function does it should be described with the function definition.

  • Other programmers should be able to take the object file and the header file of your module and use your module successfully.

Preventing Multiple Header File Inclusion

• A header file can include another header file.

• Example: one.h contains a definition of a data type that is used in two.h. When one.cpp (or two.cpp) is compiled, one.h is included twice.

• If the header file only contains function prototypes, it can safely be included more than once. But type or class definitions cannot appear more than once.

• Solution: use #ifndef and #define preprocessor directives.
  • The #define directive defines a value for the preprocessor.

  • The #ifndef directive causes the preprocessor to allow the compiler to compile a section of code only if a value has not been defined. (There is also a #ifdef directive.)

• Example: The first time the preprocessor goes through a header file, a value will be defined. On subsequent passes through the file, the contents of the file will be ignored.

• I expect you to use this technique on all your header files.

Function Overloading

• Function overloading is when the same name is used for more than one function. Function overloading is also called function polymorphism. (Do not confuse function polymorphism with object polymorphism, which we will see later.)

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