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POINERS TO FUNCTIONS

eliahu c. over 11 years ago

Hi
What is the point of using pointers to functions in C ?
Why not call directly a function ?

Thanks
Elico

Parents

0 Ash J over 11 years ago in reply to Andy Neil

consider a situation where you have an uart or a keypad from where the user is going to give input commands at runtime. depending upon the commands, the functions will be executed.

under such a case you will have a very big if-else (alternatively switch-case) statement.


if(input_cmd == 0x01)
function1();
else if(input_cmd == 0x02)
function2();
else if(input_cmd == 0x03)
function3();

...

else if(input_cmd == 0xFF)
function255();               // The list will be very long, clumsy, unorganized, poor readability

on contrary, consider an array of function

CMDS_Functn FunctionArray1[256] = {
                        /*00-07*/        (*NotDef),(*funtion1),(*function2),(*function3), ...
                        /*F7-FF*/        (*function254), (*function255)};


//functions can be called as
Cur_Func = FunctionArray1[input_cmd].Cur_FunctnPtr;     //Load current Function Pointer
        (*Cur_Func)();

Reply

0 Ash J over 11 years ago in reply to Andy Neil

consider a situation where you have an uart or a keypad from where the user is going to give input commands at runtime. depending upon the commands, the functions will be executed.

under such a case you will have a very big if-else (alternatively switch-case) statement.


if(input_cmd == 0x01)
function1();
else if(input_cmd == 0x02)
function2();
else if(input_cmd == 0x03)
function3();

...

else if(input_cmd == 0xFF)
function255();               // The list will be very long, clumsy, unorganized, poor readability

on contrary, consider an array of function

CMDS_Functn FunctionArray1[256] = {
                        /*00-07*/        (*NotDef),(*funtion1),(*function2),(*function3), ...
                        /*F7-FF*/        (*function254), (*function255)};


//functions can be called as
Cur_Func = FunctionArray1[input_cmd].Cur_FunctnPtr;     //Load current Function Pointer
        (*Cur_Func)();

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