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Simple cpp summation program

I am trying to get a C ++ program that a user enters:

#include <iostream>

int main(){
        int sum = 0, value = 0;
        // read until end-of-file, calculating a running total of all values read
        while (std::cin >> value){
                sum += value;
        }
        std::cout << "Sum is: " << sum << std::endl;
        return 0;
}

I read this example in C ++ primer, but when I compile this program and run it, the request keeps waiting for input. Why doesn't it output anything?

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2 answers


std::cin

keeps waiting for input until it finds EOF

(end of file). When you run it in terminal (Linux) you just need to press Ctrl+ Dto generate EOF

. If you are a Windows user use Ctrl+ Z.



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Set the values limit

and test it in a while loop.

Let me add some code to illustrate ...

#include <iostream>

int main(){
        int sum = 0, value = 0, limit=5, entries=0;
        std::cout << "Enter "<< limit << " digits:"; 
        // read until end-of-file, calculating a running total of all values read
        while ((std::cin >> value) && (entries < limit) ){
                sum += value;
                entries++;
        }
        std::cout << "Sum is: " << sum << std::endl;
        return 0;
}


another option is to take the number of records the user is going to give;

#include <iostream>

int main(){
        int sum = 0, value = 0, limit=0, entries=0;
        std::cout << "Enter limit:";
        std::cin >> limit;
        // read until end-of-file, calculating a running total of all values read
        while ((std::cin >> value) && (entries < limit) ){
                sum += value;
                entries++;
        }
        std::cout << "Sum is: " << sum << std::endl;
        return 0;
}
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