How do I use functions like this? ( C++, operator overloading)

Question

#include <iostream>
using namespace std;

class VectorND
{
public:
    int N;
    VectorND(int n)
        :N(n) {}

    float *vec_value = new float[N];

    void assignValue(int i, float v)
        {
            vec_value[i] = v;
        }

};

This is my code and I'm trying to solve this problem, but I do not know what to do.

Problem 4. Implement operator overloading of VectorND class for the following operations.
my_vec.assignValue(3) = 10;

std::cout << my_vec(3);
Example
int main(void)
{
  VectorND my_vec(10);
    my_vec.assignValue(3) = 10;
    std::cout << my_vec(3);

    return 0;
}

Output : 10

I've read the explanation of operator overloading, but I do not know how to apply it to this problem. — DW7, Dec 09 '17 at 13:27
@DW7 _"I've read the explanation of operator overloading, but I do not know how to apply it to this problem."_ You're right in so far that the function call operator syntax is poorly covered in that Q&A I proposed as duplicate. I'll edit the relevant part. — user0042, Dec 09 '17 at 13:54
@DW7 I hope [that's](https://stackoverflow.com/a/4421719/8242698) clearer now. — user0042, Dec 09 '17 at 13:59

Jake Freeman · Accepted Answer · 2017-12-09T13:51:34.573

-1

For the first operator overload you have to do something like this:

float& operator () (int i)
{
    return vec_value[i];
}

When you do myVec(3) = 4;, the myVec(3) returns a reference to the float at the index 3 which you then assign to 4.

For myVec.assign(3) = 10 you should overload the assign method to take an index and return a reference to a float for that index.

For the second one it is more complicated you have to do a declaration in your class friend ostream& operator << (ostream& n, VectorND& myVec);

Then outside the class:

ostream& operator<<(ostream& n, const VectorND& myVec)
{
   // This just pushes all the values to the stream
   for(int i = 0; i< N; i++) cout<<vec_value[i]<<endl;
}

edited Dec 09 '17 at 13:51

answered Dec 09 '17 at 13:33

Jake Freeman

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`VectorND& myVec` should be `const VectorND& myVec` in the output operator overload. – user0042 Dec 09 '17 at 13:47
@user0042 You are right that is the best practice – Jake Freeman Dec 09 '17 at 13:51
Wow, I really appreciate it. You're the god of coding. – DW7 Dec 09 '17 at 14:12
If it works don't forget to upvote and accept @DW7 – Jake Freeman Dec 09 '17 at 14:13
@JakeFreeman You should have better gone my course of action here. – user0042 Dec 09 '17 at 14:46
@user0042 I used your suggestion and I recognize that it was correct. – Jake Freeman Dec 09 '17 at 14:48
@JakeFreeman No, no. I meant you should have rather improved the answer in the duplicate instead of writing a new one. – user0042 Dec 09 '17 at 14:49
@user0042 my answer is the only one for this question, I guess I am not understanding what you are trying to say. – Jake Freeman Dec 09 '17 at 14:58
@JakeFreeman https://stackoverflow.com/questions/47728965/how-do-i-use-functions-like-this-c-operator-overloading/47729100?noredirect=1#comment82419084_47728965 – user0042 Dec 09 '17 at 14:59
Ok I will edit the original to incorporate this @user0042 – Jake Freeman Dec 09 '17 at 15:21

How do I use functions like this? ( C++, operator overloading)

1 Answers1