Passing function to function C

Question

im currently training myself in passing functions as parameters, but i cant get my logic to work. Hope one of you can help!

I have a function called 'square' which takes an int and returns the square of it.

Then i have another function called 'map', which takes a list of numbers and the square function as input, and i'd like to square each of these numbers in the map function.

I declare my pointer to square function in main, but since it takes an int as parameter, it just squares that initial integer for all the numbers in my list. How do i assign my function to a variable, in a way such as when i pass it to the map function, i can change what int gets passed to the square function

int b = 1; //Global variable

int square (int x) {
  return x*x;
}
int map (struct node *head, int x) {
int z = head->data; //this variable is what i want squared.

// If i call x here itll use the b variable and square that. 
//changing b doesnt work either since it takes the value that b had when map function was called
if (head->next == NULL) {
    return 0;
  }
  else {
    printf("Value: %d", z)
    map(head->next, x);

  }
  return 0;
}

int main(void) {
int (*sf)(int); 
sf = square; //Assigning the square function to the sf variable
int x =(*sf)(b); //here is the problem, b is the variable thatll get squared every time my function runs
map(head,x); //passing x (square function) and head of a linked list

It would help to additionally include the definition of `struct node` — h0r53, Nov 11 '19 at 20:13
You say you're passing a function into map(), but you're not. Map is only receiving a list and an int. — Lee Daniel Crocker, Nov 11 '19 at 20:14
You need to pass `sf` to `map`. The `x` variable in `main` is useless. — user3386109, Nov 11 '19 at 20:15
@user3386109 How would i go about doing that exactly? What type of argument should my map function take? — Drax, Nov 11 '19 at 20:29
https://stackoverflow.com/a/9413/1472660 Check this answer. It shows you how to define a function that takes a function as a parameter. — Andy Foster, Nov 11 '19 at 20:49
The map function would be `int map(struct node *head, int (*func)(int))` — user3386109, Nov 11 '19 at 20:49

Passing function to function C

0 Answers0