C++ - Overloaded += Operators

Question

I'm attempting to overload a += operator with the following line:

a = b += c += 100.01;

but my second += in that code shows an error as it matches no implementation i guess?

Heres my full relevant code:

main.cpp:

 #include <iostream>
 #include "Account.h"

using namespace sict;

void displayABC(const Account& a, const Account& b, const Account& c)
{
    std::cout << "A: " << a << std::endl << "B: " << b << std::endl
    << "C: " << c << std::endl << "--------" << std::endl;
}

int main()
{
    Account a("No Name");
    Account b("Saving", 10000.99);
    Account c("Checking", 100.99);
    displayABC(a, b, c);
    a = b + c;
    displayABC(a, b, c);
    a = "Joint";
    displayABC(a, b, c);
    a = b += c;
    displayABC(a, b, c);
    a = b += c += 100.01;
    displayABC(a, b, c);

    return 0;
}

Account.h (Relevant definitions)

class Account{

    public:
        friend Account operator+(const Account &p1, const Account &p2);
        Account& operator+=(Account& s1);
        Account & operator=(const char name[]);
        friend double & operator+=(double & Q, Account & A);
        Account & operator=(Account D);

    };
    Account operator+(const Account &p1, const Account &p2);
    double operator+=(double& d, const Account& a);

};

Account.cpp (relevant implementations)

Account& Account::operator+=(Account &s1) {
        double b = this->balance_ + s1.balance_;
        this->balance_ = b;
        return *this;

    }
    Account & Account::operator=(Account D) {
        strcpy(name_, D.name_ );
        this->balance_ = D.balance_;
        return *this;

    }
    Account & Account::operator=(const char name[])
    {
        strcpy_s(name_, name);
        return *this;
    }


    double & operator+=(double & Q, Account & A)
    {
        Q = Q + A.balance_;
        return Q;
    }

So my question is, how do i change my implementations correctly to run this function: a = b += c += 100.01;

Thank you.

Answer 1

In this statement

a = b += c += 100.01;

at first expression

c += 100.01

is evaluated. However the class does not have a corresponding overloaded operator.

On the other hand if the class has a conversion constructor that converts an object of type double to type Account nevertheless the corresponding operatpr += should be declared like

Account& operator+=(const Account& s1);
                    ^^^^^ 

Also take into account that these declarations

friend double & operator+=(double & Q, Account & A);

and

double operator+=(double& d, const Account& a);

differ.