using function pointer in program

Question

I have used function pointer in this, but not able to understand why it is not working, here is my piece of code. when i run this code i get not output, i was expecting Decending order and Ascending order to be printed when i give -r in command line, and if no command line input is given it should print ascending order.

What has gone wrong in my code ??

#include <stdio.h>
#include <stdlib.h>

void decending_sort()   {
   printf ("Decending order \n");
}

void ascending_sort()   {
  printf ("Ascending order \n");
}

int main( int argc, char **argv)  {

int i;
void (*sort)();

while (*++argv) {
    if ((strcmp ( *argv, "-r" )) == 0)
        sort = decending_sort;
}
sort = ascending_sort;
}

I don't see a call to sort.

Kiril Kirov
– Kiril Kirov

2014-02-21 14:26:52 +00:00
Commented Feb 21, 2014 at 14:26 — Kiril Kirov
– Kiril Kirov, Commented Feb 21, 2014 at 14:26

alk · Accepted Answer · 2014-02-21 14:27:10Z

5

You define sort as function variable, assign a value to it, but never call it, so neither decending_sort() nor ascending_sort() is ever executed.

To invoke it add this last line to `main()

  [...]

  sort();
}

Also: Functions without any parameters shall be declared like this:

void decending_sort(void);

Either should be a variable of their type

void (*sort)(void);

answered Feb 21, 2014 at 14:27

alk

71.2k10 gold badges112 silver badges274 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user3336874 Over a year ago

Why should i need to add sort(); line in main, i have created a function pointer and am passing the address of the function to it, it should automatically switch to that function right. Can you please explain

alk Over a year ago

@user3336874: Telling the machine that an address of some function is tobe stored somewhere (as done by assigning something to sort) does not yet tell the machine to execute the code at that address.

Natasha Dutta Over a year ago

@user3336874 assigning is fine, but as long as you are not calling the function using sort(), how it will be executed?

Collectives™ on Stack Overflow

using function pointer in program

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related