(C++)++ Course

The rand() Function

4/10

I want to point out that SoloLearn did a good job on explaining how to get random numbers, but there is more here than one might realize. I only point this out because I have seen a code where what I'm about to explain wasn't understood. You DO NOT need to place srand(time(NULL)) in every function in which you want to use random numbers. One time inside the main function and you can use rand() in every other function.

void func() {
    // this is not needed
    srand(time(NULL));
    cout << rand() % 100 << endl;
}

int main() {
    srand(time(NULL));// once here is enough
    func();
    return 0;
}

Default Arguments

4/10

When going through this module without having some experience writing functions, it may be difficult to catch what SoloLearn did. If you look at the last part of this module, you can see the function they wrote with default values l, w, and h, but notice how they called it in main:

int main() {
    cout << volume() << endl;
    cout << volume(5) << endl;
    cout << volume(2, 3) << endl;
    cout << volume(3, 7, 6) << endl;
    return 0;
}

Because of the way you call a function, you can't pass in values for the first and the last argument without also passing in the middle argument, so use this knowledge when you're writing your functions; put the default values at the end.

Passing Arrays to Functions

8/10

Just a note on passing arrays to functions: you don't have to pass the size of the array if you don't want to. You can use the sizeof function that SoloLearn mentioned in an earlier module of this course:

void printArr(int arr[]) {
    int sz = sizeof(arr) / sizeof(int);
    for (int i = 0; i < sz; ++i) {
        cout << arr[i] << " ";
    }
}

Pass by Reference with Pointers

9/10

SoloLearn mentions that you can pass by reference using pointers, but they forget to mention that you can also just pass by reference (not using pointers). Here is how you can do that:

void change(int &a) {// notice the &
    a = 100;
}

int main() {
    int x = 50;
    change(x);
    cout << x << endl;
}

100

I don't use references very commonly, except for when I'm passing by reference to a function, but you may find them very useful in other ways. You can use them like this as well:

int main() {
    int a = 50;
    int b = &a;// changing b will now change a
}

C++ Course, Functions