C函数，使用指针代替返回

Question

I have this function:

void update(int something, int nothing) {
    something = something+4;
    nothing = 3;
}

And then the function call:

int something = 2;
int nothing = 2;

update(something, nothing);

Inside the function, something would be 6 and nothing would be 3, but because we do not return anything, the values does not change.

For just one value, I could use the return-value from the function, but now I think that I have to use pointers, right?

I want both the something and the nothing to be returned from the function so I could use the new values after the function call, how do I do that? :)

Answer 1

Send values using & and receive them using *

Example:

void update(int* something, int* nothing) {
    *something = *something+4;
    *nothing = 3;
}

int something = 2;
int nothing = 2;

update(&something, &nothing);

Two years without using C, but I think this is correct.

Answer 2

What you want to do is referencing and dereferencing the variables. By calling &variable you get the pointer to that variable, by calling *variable you get, what this variable points to. Here you can get more information about pointers.

void update(int* something, int* nothing) {
    *something = *something+4
    *nothing = 3
}

int something = 2;
int nothing = 2;

update(&something, &nothing);

this is what you want, but it isn't the best style, as people that don't know the code could not understand what you are doing. What I mean by that is, that you should not modify parameter variables as long as it is not really needed. Most functions can be written without such behaviour.

If you really need to "return" two variables, this is what I would do:

int update(int something, int* nothing) {
    something += 4;
    *nothing = 3;
    return something;
}

int something = 2;
int nothing = 2;

something = update(something, &nothing);

Answer 3

Use the blow Code:

1)

  void update(int * something, int * nothing) 
    {
        *something = *something + 4;
        *nothing = 3;
    }

    int something = 2;
    int nothing   = 2;

    update(&something, &nothing);

It means you are passing the address of the variable into function update, and changing the value inside the address.

OR

2) make both something, nothing global variable. That also should work. But it is not a good solution.