What Is The Difference Between An Inline Function And A Macro?

A statement or a group statements(function) which are oftenly used in a program can be written in the form of a function whitch is nothing but a MACRO.

eg:   #define  pi  3.14  

It is a single line macro.If you want to use 3.14 any where in the program u can simply use 'pi', then pre processor assigns 3.14 to the 'pi' while exicuting a program.

coming to IN LINE FUNCTION  it is also a macro,but it has aditional properties like

1.if u write a big function as a inline function pre processor assumes it  like a normal function  (why  because  generaly inline functions or macros  are used to reduse the switching time between the functions)  automatically.That means while writing an inline function it is a request to the pre-processor but not an order.

It's possible to define a macro to expand into the same code that an inline function would execute.  But the macro would be limited to direct use in expressions--a macro cannot be called with apply, mapcar and so on. Also, it takes some work to convert an ordinary function into a macro. To convert it into an inline function is very easy; simply replace defun with defsubst. Since each argument of an inline function is evaluated exactly once, you needn't worry about how many times the body uses the arguments, as you do for macros.