CODEWITHSUNDEEP
c++function
Mitchell Kelly
Mitchell Kelly

Reputation: 23

Why is this function not adding one to an int called number?

Why is this code not adding one to the int numbers?

Forgive me for posting a very easy question, I am new to c++.

The value of numbers seem to be unaffected when appearing in the console. Am I incorrectly passing the function's argument?

#include <iostream>
    
    int number = 0;
    int addOne(int a);
    
    int main()
    {
    
        std::cout << "Please type a number to add to one: ";
        std::cin >> number;
        std::cout << number << " plus one equals: ";
        int addOne(number);
        std::cout << number;
       
    }
    
    
    int addOne(int a) {
        
        return a++;
    
    }

Upvotes: 1

Views: 217

Answers (3)

quetzalcoatl
quetzalcoatl

Reputation: 33526

One more possibility, your function already returns value.
Why not use it?

int addOne(int a) { // no &, still passed as copy
    a++;    // increase the copy
    return a;   // return value AFTER increase has been done on 'a'
}

number = 2;
number = addOne(number); // copy in (2), copy out (3)
std::cout << number; // now it's 3

Upvotes: 1

Ziad Adeela
Ziad Adeela

Reputation: 496

You're passing the variable by value, which means that the value inside the function will be a copy and the original value will not be modified.

Upvotes: 1

MikeCAT
MikeCAT

Reputation: 75062

Function arguments are copied by default, so modifying the copy (in this case a) won't affect the original (in this case number).

To have functions modify caller's variables, you should use reference.

Also note that int addOne(number); in your main function is not a function call but a declaration of a variable addOne with initializing it to number.

#include <iostream>

int number = 0;
int addOne(int& a); // add "&"

int main()
{

    std::cout << "Please type a number to add to one: ";
    std::cin >> number;
    std::cout << number << " plus one equals: ";
    addOne(number); // remove "int"
    std::cout << number;
   
}


int addOne(int& a) { // add "&"
    
    return a++;

}

Upvotes: 2

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