I'm trying to write a program that reads in positive float numbers from the user and then when the user's is a negative number, gives the average of the numbers, excluding the negative.

#include <iostream>
using namespace std;
int main() {
float av_number, total = 0, input;
do {
    for (int i = 1; i >= 1; i =   i) {
        cout << "Please input a number: ";
        cin >> input;
        total = total  = input;
        av_number = total / i;
        cout << av_number << endl;
        break;
    }
} while (input >= 0);
cout << av_number << endl;
}   

When I run this, the program simply adds the inputs together on each line, and then subtracts my final negative input before closing the program. If I were to guess, It's likely a logical confliction within my sequence of do & for loops, but I'm unable to identify the issue. I may have also misused i in some fashion, but I'm not certain precisely how. Any help would be appreciated as I'm still learning, Cheers!

CodePudding user response：

• you don't need the for loop, you just need some iterator to count the number of entered numbers, so you can delete that for loop and use a counter variable instead.

• also, you are breaking in the loop without checking if the input < 0, so you can write this

  if (input < 0)
       break;
  

• also, you shouldn't calculate av_number = total / counter; except only after the end of the big while loop

• it's total = input; not total = total = input;

• writing while (input >= 0) wouldn't make sense as long as you are breaking inside the loop when input < 0, so you can write while (true); instead

and this is the code edited:

#include <iostream>
using namespace std;
int main() {
    float av_number = 1.0, total = 1, input = 1.0;
    int counter = 0;


    do {
        cout << "Please input a number: ";
        cin >> input;

        if (input < 0)
            break;

        counter  ;
        total  = input;

    } while (true);
    av_number = total / counter;
    cout << av_number << endl;
}

and this is the output:

Please input a number: 5
Please input a number: 12
Please input a number: 7
Please input a number: -2
8

P.S : read more about Why is "using namespace std;" considered bad practice?

CodePudding user response：

You should move the calculation of the average value out of the loop where the adding takes place and only add non-negative values to total.

#include <iostream>

int main() {
    float total = 0.f;
    int i = 0;

    // loop for as long as the user successfully enters a non-negative value:
    for (float input; std::cout << "Please input a number: " &&
                      std::cin >> input && !(input < 0.f);   i)
    {
        // now `input` is non-negative
        total  = input; // and only sum it up here, no average calculation
    }

    if (i > 0) { // avoid division by zero
        // finally calculate the average:
        float av_number = total / i;

        std::cout << av_number << '\n';
    }
}