Function pointer

2.  Pointers point to the address of a function
 A running program is allocated a certain space in the main memory
 The executable compiled program code and the used variables
are both put inside this memory
 Thus a function in the program code has an address.
 Can be declared, assigned values, and then used to access the functions
they point to

4. int add(int,int);
int *add(int,int);
a function add with one argument of int
type and return value of int * (i.e. integer
pointer)

5. int add(int,int);
int *add(int,int);
int (*add)(int,int);

7.  Must be initialized prior to use
 Assign the address of a function to a function pointer
Simply uses the name of a function
Optional to use the address operator & in front of the
function’s name

8.  Must be initialized prior to use
int add(int,int);
fpointer = add;
Names of these functions, add - pointers
to those functions

10. Two ways
 Use the name of the function pointer instead of the
name of the function
 Explicitly dereference it
result1 = fpointer(4, 5);
Function cannot be
passed as parameter to
another function

11. #include <stdio.h>
/*Define a pointer to a function */
int(*fpointer)(int, int);
int add(int a, int b){return(a + b);}
int sub(int a, int b) {return(a - b);}
int main(){
fpointer = &add;
printf("%d n", fpointer(4, 5));
fpointer = sub; // Function’s name can also be used to get functions’address
printf(“%d n”, (*fpointer)(6, 2));
return 0;
}

13. #include <stdio.h>
int add(int a, int b)
{
return a+b;
}
int sub(int a, int b)
{
return a-b;
}
int arith(int f(int,int))
{
int x=5, y=4,s;
s=(*f)(x,y)
return s;
}
int main()
{
printf("n Add: %d",arith(add));
printf("n Sub: %d",arith(sub));
return 0;
}

14. #include <stdio.h>
int even(int a)
{
if(a%2==0)
return a;
else
return 0;
}
int odd(int a)
{
if(a%2!=0)
return a;
else
return 0;
}
int sum(int f(int), int m, int n)
{
int s = 0;
for(int i=m; i<=n;++i)
s+=f(i); or s+=(*f)(i);
return s;
}
int main()
{
printf("n Sum of Even numbers: %d",sum(even,5,10));
printf("n Sum of Odd numbers: %d",sum(odd,5,10));
return 0;
}

16. #include <stdio.h>
int add(int x,int y)
{
return x + y;
}
int sub(int x,int y)
{
return x - y;
}
int (*getOperator(const char oper))(int, int)
{
if(oper == '+') return &add;
if(oper == '-') return &sub;
}
int main()
{
int x = 20,y = 10,z = 0;
int (*func)(int, int);
func = getOperator('+');
z = func(x,y);
printf("Add : %dn",z);
func = getOperator('-');
z = func(x,y);
printf("Sub : %dn",z);
return 0;
}

17. #include <stdio.h>
#include <stdlib.h>
typedef int(*pfOperator)(int, int);
int add(int x,int y)
{
return x + y;
}
int sub(int x,int y)
{
return x - y;
}
pfOperator getOperator(const char oper)
{
if(oper == '+') return &add;
if(oper == '-') return &sub;
}
int main()
{
int x = 20,y = 10,z = 0;
pfOperator func = NULL;
func = getOperator('+');
z = func(x,y);
printf("Add : %dn",z);
func = getOperator('-');
z = func(x,y);
printf("Sub : %dn",z);
return 0;
}

19. #include <stdio.h>
int(*fpointer[2])(int, int);
int add(int a, int b){return(a + b);}
int sub(int a, int b) {return(a - b);}
int main(){
fpointer[0] = &add;
printf("%d n", (*fpointer[0])(4, 5));
fpointer[1] = sub;
printf(“%d n”, fpointer[1](6, 2));
return 0;}