Container to save function pointer - c

Question

I need a container to save function pointers to certain numbers.
Like
1 = function add
2 = function sub
3 = function mult
And so on. This is for a simple interrupt handler, where depending on the interrupt number a certain function should be called.
I thought that I can do this with a structured list, but I know the size of the maximal amount of entries. So I thought about an array of strings like
const char *functions[2];
a[0] = "add";
a[1] = "sub";
But then I don't know how I can further use the strings.
Any tips or thoughts?
Thanks in advance!
EDIT: To clarify, I have 2 important functions here, one, where I want to save a function pointer together with a number into some container. And another one, which just says "goto the function which is at a certain number in that container". So the first function gets an int number (say from 1 to 50) and a pointer to a function. Those should be saved together. The second function then just gets an int number as parameter and then it should call the function which is associated with that int number in my container. What I'm asking is how I could save a pointer that points to a function together with a number.
EDIT2: I do want to save function pointers. I thought I could maybe save the function name as a string and then use it later as function name because I didn't know another way.

Answer 1

If you want to store and use a function pointer you can do it like this:
// the functions you want to point to
int add(int a, int b) { do stuff }
int sub(int a, int b) { do some other stuff }
...
// declare and set a function pointer
int (*myFuncPtr) (int, int);
myFuncPtr = ⊂ // points to the function "sub". The & is optional
// now use it:
int result = myFuncPtr(23, 42);
The type of a function pointer depends on the return value and the parameters of the function you want to point to.
You can make the declaration of a function pointer variable easier
by using typedef:
typedef int (*funcPtr) (int, int);
Now declare and initialize a function pointer using the typedef like this:
funcPtr myFuncPtr = &add;
Of course you can now put many of those pointers into an array
and access them by the indices:
funcPtr funcPtrs[] = { &sub, add }; // like i said, the ampersand is optional
int result = funcPtrs[0](23, 42);

Answer 2

You have to store function pointers, so define a new function pointer type and make an array. According to your question the all functions should take two int parameters and return and int, so the new type should be something like this:
typedef int (*operation_t)(int,int);
Now you can create an array of operation_t. The whole code:
#include <stdio.h>
typedef int (*operation_t)(int,int);
int addInt(int n, int m) {
return n+m;
}
int subInt(int n, int m) {
return n-m;
}
int multipleInt(int n, int m) {
return n*m;
}
int main ()
{
const operation_t function_list[3] = {&addInt, &subInt, &multipleInt};
int i;
for(i = 0; i < 3; i++)
{
printf("inputs: 2 and 3 result: %d\n", function_list[i](2,3));
}
return 0;
}
The output:
Note that, as it's an array the indexes are 0, 1, 2.
To add an own ID you can create a stuct with the function pointer and an int ID.
typedef struct operation
{
int (*operation_p)(int,int);
int id;
} math_operation_t;
You can even build a linked list, and add functions dynamically if you define a third member variable, which should be the pointer to the next element.