How to overload the '+' operator to add a float to a class and return a float(C++)?

Question

I have a class called Sensors that has a variable called 'value' which is a float. I want to be able to re-write the following:

averageTemperature = averageTemperature + sensors[count].value;// sensors is an array of Sensors object

to 

averageTemperature = averageTemperature + sensors[count];

//averageTemperature is also a float.

So far I have done this:

class Sensors

{

public:

// alot of other code here

float getValue()const { return value; }

friend float operator + (float fl1,const Sensors& sensor1);// float+class=float

protected:

float value{};

};

float operator+(float fl1, const Sensors& sensor1)

{return fl1+sensor1.getValue();}

As you can see there is a problem i.e a friend function has to be used. Is there anyway around this.(I have no idea why the formatting has gone wrong!)

Answer 1

class Sensors
{
public:
    // alot of other code here
    float getValue()const { return value; }

    // define  operator+  for    Sensors+float
    float operator+(float fl1) const { return fl1 + value; }

protected:
    float value{};
};

//  define  operator+  for  float+Sensors
float operator+(float fl1, const Sensors& sensor1) {
    return sensor1 + fl1;   // call member func
}

Answer 2

Your code works fine. You just have to keep in mind that you defined overloading for float + Sensors, and not (yet) for Sensors + float.

#include <iostream>

class Sensors
{
protected:
    float value;
    
public:
    Sensors(float initValue) : value(initValue) { }
    float getValue() const { return value; }
    friend float operator + (float fl1, const Sensors& sensor1) { return fl1 + sensor1.getValue(); }
};

int main()
{
    Sensors sensor(2);
    std::cout << (3 + sensor) << std::endl; // Runs fine
    //std::cout << (sensor + 3) << std::endl; // Compilation error
    return 0;
}

Question: are you sure that Sensors + float should produce a float and not a Sensors?! Normally, it should be a latter with a float cast operator overwritten as well so Sensors can stand in for floats.

Comments

Yes. I wanted to make a float which would equal a float added to the value inside the Sensors class. so my code works like this float= float+sensors.value but will it work like this float= sensors.value+float?

---

As long as you have the

float operator + (float, const Sensors &)

function (operator overload), you can write expressions like

float = float + Sensors

OR

float = float + Sensors.getValue().

---

thanks man, I understood that!