CODEWITHSUNDEEP
c++
Buster023
Buster023

Reputation: 9

Returning and outputting 2 integers from 1 function

i have to write a code that has a function that takes two integers and returns x as (a + b) and y as (a * b) and when i run it, it only outputs y. Why doesnt it output (or return) x?

#include <iostream>
using namespace std;

int math (int a, int b) {
    int x, y;

    x = a + b;
    y = a * b;

    return x, y;
}

int main() {

    cout << math (5,3);

    getchar();
    getchar();

    return 0;
}

Upvotes: 0

Views: 91

Answers (4)

James Kanze
James Kanze

Reputation: 153929

There are two ways to make a function return more than one value. The first is to use out parameters, either references or pointers:

void
math( int a, int b, int& sum, int& product )
{
    sum = a + b;
    product = a * b;
}

int
main()
{
    int s;
    int p;
    math(5, 3, s, p);
    std::cout << s << ' ' << p << std::endl;
    return 0;
}

The other is to define a class to contain the two values:

struct MathResults
{
    int sum;
    int product;
};

MathResults
math( int a, int b )
{
    return MathResults{ a + b, a * b };
}

std::ostream&
operator<<( std::ostream& dest, MathResults const& value )
{
    dest << value.sum << ' ' << value.product;
}

int
main()
{
    std::cout << math( 5, 3 ) << std::endl;
    return 0;
}

In most cases, the second solution is to be preferred.

Upvotes: 0

Evan Carslake
Evan Carslake

Reputation: 2359

You can only return one thing. You can put those in a struct, and return it. Simpler example.

struct xy {
    int x;
    int y;
};

xy math(int a, int b) {
    xy pair;
    int x, y;
    pair.x = a + b;
    pair.y = a * b;    
    return pair;
}

Upvotes: 0

NPE
NPE

Reputation: 500377

The return type of math is int, so this is what it returns (a single integer).

The expression x, y uses the comma operator. The comma operator evaluates x, discards its value, and then evaluates and returns y. In other words, return x, y is equivalent to return y.

You could use std::pair<int,int> to return a pair of integers.

Upvotes: 3

frsfnrrg
frsfnrrg

Reputation: 136

The line

return x, y;

does not do what you expect. The comma operator returns only the value after the last comma - in this case, y. To return multiple values, you should use a struct or class containing both.

Upvotes: 1

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