When is a function not a function?
Short functions which are called frequently
are often declared as inline. Accessors
and mutators are prime examples of functions which
are candidates to be inline.
When the compiler sees a function call to an inline
function, it replaces the function call with the
code in the body of the function. The original
code looks like a function call, but no function call
is actually made at runtime.
How do I create an inline function?
To declare a function inline, precede the function declaration
and function defintion
with the keyword inline.
Any member function whose code is written in the
class definition is automatically considered inline.
Because the compiler needs to have access to the body of the
inline function, the inline function must be written or #included in the
Bob ( void );
// an implicit inline function
int GetSize( void ) const
// explicitly inline below
void SetSize( int size ) ;
// explict inline SetSize
inline void Bob::SetSize( int size )
m_size = size;
// inline non-member function
inline void PrintBob ( const Bob& bob )
cout << bob.GetSize( ) << endl;
Notice that the constructor and other member functions which are
not inline would be defined in the .cpp file.
To make the code a bit easier to read, we prefer to define
the functions outide the class definition (like SetSize())
rather than in the class definition (like GetSize( )).
Also note that declaring a function inline is just a recommendation
to the compiler which it may choose to ignore.
All of this sounds great. Is there a downside? Of course.
- Inline functions mix implementation and defintion in the header file
- Inline functions may make your executable bigger
Last Modified: Monday, 28-Aug-2006 10:16:07 EDT