(From http)
Inline functions
Inline functions are functions where the call is made to inline functions. The actual code then gets placed in the calling program.
Inline functions eliminate function-call overhead. The programmer uses the key word inline to advise the compiler to generate function code in line (when possible ) to minimize function calls. The compiler could choose to ignore the inline advice.
The inline qualifier should be sued only with small, frequently used functions.
Member functions defined in a class definition are automatically inlined. The compiler reserves the right not to inline any function.
