C Programming - Functions - Discussion

No one is mentioning about pointer function.

#include<stdio.h>
int fun(int, int);
typedef int (*pf) (int, int);//Here pf is a pointer of type function.

/*It means pf could point to any function that would a return value of int and would accept 2 args of type int*/

int proc(pf, int, int);

int main()
{
printf("%d\n", proc(fun, 6, 6));

/*Here the address of fun is passed to the called function proc*/

return 0;
}
int fun(int a, int b)
{
return (a==b);//return(1)

//As a==b it will return a bool value i.e. true value=1.

}
int proc(pf p, int a, int b)

/*Now proc args are pf p i.e.a pointer to function .it means pf has the address of fun and now it will call the fun function*/
{
return ((*p)(a, b));
}

proc is indirectly calling fun via a function pointer.

The arguments that fun receives are again 6 and 6, and the equality operator evaluates to an int with the value 1 because they are equal.

If they were not equal, the == operator would yield 0.

What is pf p. Let any one explain me?

Return statement only returns one value.

Simply. Return statement only returns one value i.e. rightmost value.

@Ashish.

#include<stdio.h>
int fun(int);
typedef int (*pf) (int, int);
int proc(pf, int, int);

int main()
{
printf("%d\n", proc(fun, 6,6));
return 0;
}
int fun(int a)
{
return (a=9);
}
int proc(pf p, int a, int b)
{
return ((*p)(a, b));
}

Guys please help me out ...this program is returning 9 as output how it is possible? bcoz pf is defined as taking 2 variables of type int and returning an int..but in this program i mentioned only a function fun with single argument.so as i think program must show error but it is providing a output 9.can someone tell me how it is possible?????????


In c there is no strict checking in compilation time it means that u can pass 1 value during the function calling time or at receiving time function parameter once time a program has been compiled by compiled so it would run....

int fun(int a)
{
return (a=9); //a is assigned to 9 not compared.
}

proc(fun, 6,6)// it would be changed as proc(address of fun, 6,6)

Address of fun containing the value of a=9

Simple:
The return statement in proc function is replaced like this:
return( fun(a,b));
Which means calling the function fun(a,b).
Since it returns a==b and integer value of true is 1, the output is 1.

Thank you vishwas.

Excellent answer!!Vishwas

Thanks vishwas.