C++ - 用另一个替换数组的 int 元素

Question

I've been going through the Fourth Edition of C++ Primer, and I'm on a pointer exercise right now. The exercise asks to make a program to go through an array and replace the elements with 0. I have this so far:

#include <iostream>

using namespace std;

using std::cout;
using std::endl;

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    for (int i = 0; i != 5; i++)
        arr[i] = 0;
        cout << arr[i] << endl;
}

But I'm getting an error:

name lookup of 'i' changed for ISO 'for' scoping

How do I change the element?

Answer 1

your loop should go like this:

for (int i = 0; i != 5; i++) {
  arr[i] = 0;
  cout << arr[i] << endl;
}

I also recommend you put return 0; before the final } .

Answer 2

for (int i = 0; i != 5; i++)
    arr[i] = 0;
    cout << arr[i] << endl;

You forgot { and } . This means that the line starting cout is not presently part of the loop and, thus, i is out of scope.

The error is a little misleading because it's focusing on the point that this used to be valid, many many many years ago.

But unlike some other languages, block scope is defined by { and } and not by indentation. Thus, write:

for (int i = 0; i != 5; i++) {
    arr[i] = 0;
    cout << arr[i] << endl;
}

for great success.

Answer 3

Well, it should be like this instead: Remember the 5 elements only go from array indices 0 to 4 !

#include <iostream>

using namespace std;

using std::cout;
using std::endl;

int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    for (int i = 0; i < 5; i++){
        arr[i] = 0;
        cout << arr[i] << endl;
    }
}

Change the != to < and add the Curly brackets for the for loop.

Answer 4

Your for loop is missing it's body. You need curly braces around

arr[i] = 0;
cout << arr[i] << endl;

so the compiler knows that code is the body of the for loop.