cin command to use for inserting value on a function

Question

How could I use cin to insert values for the function?

cin >> addNumber();
cout << addNumber() << endl;

I am not sure if I used these lines above properly. What command/word or whatever it is called should I use to be able to do so? I'm trying to add a value for the variables x and y to add those two numbers and print the sum.

#include <iostream>

using namespace std;

int addNumber(int x, int y)
{
    int answer = x + y;
    return answer;
}

int main()
{   
    cin >> addNumber();
    cout << addNumber() << endl;
    return 0;
}

_'I am not sure if I used these lines above properly.'_ No they arent, unless `addNumber()` returns a valid reference to some object that can be accessed by `operator>>(istream&,...)` — πάντα ῥεῖ, May 03 '14 at 10:55

score 3 · Accepted Answer · edited May 03 '14 at 11:09

3

#include <iostream>

int addNumber(int x, int y)
{
    int answer = x + y;
    return answer;
}

int main()
{
    int x,y;
    std::cin >> x >> y;

    std::cout << addNumber(x,y) << std::endl;

    return 0;
}

edited May 03 '14 at 11:09

tommyo

531
4
10

answered May 03 '14 at 10:55

khajvah

4,889
9
41
63

Thanks, but what does "std::" means and how it is used? I've tried the code. endl seems to cause errors, why is that? It's working if I remove it. `std::cout << addNumber(x,y) << endl;` – Dave Martinez May 03 '14 at 11:00
@Rakken yes sorry, I updated the answer. cout, endl, cin are part of namespace `std`, so you have to put `std::` in front or you can put `using namespace std` at the beginning of the file, though it is not a good practice. – khajvah May 03 '14 at 11:04
That worked. One more question, you seem to have used std::cout instead of simply cout. Why is that? Can't I just simply use cout and cin rather than std::cout, std::cin? – Dave Martinez May 03 '14 at 11:10
If you put `using namespace std` in front of the file, you can use cin and cout without `std::` but it's better practice to use `std::`. take a look at [this](http://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) – khajvah May 03 '14 at 11:32

score 0 · Answer 2 · answered May 03 '14 at 11:35

#include <iostream>

using namespace std;

int addNumber(int x, int y)
{
    int answer = x + y;
    return answer;
}

int main()
{   
    int x,y;
    cout<<"Enter first number"<<endl;
    cin>>x;
    cout<<"Enter second number"<<endl;
    cin>>y;    
    cout<<addNumber(x,y)<<endl;
    return 0;
}

cin command to use for inserting value on a function

2 Answers2

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