c++ - Overloaded Operator not working properly? -

i getting error when compile program , unsure how fix appropriate function solve problem. post main, header, , cpp file below desired outcome following. help/tips appreciated, thank you!

error get:

error   c2679   binary '+=': no operator found takes right-hand operand of type 'double' 

updated: have fixed code update "=" operator overload , working except 1 line of output.

this output:

a: no name: $0.00

b: saving: $10000.99

c: checking: $100.99

---

a: no name: $10101.98

b: saving: $10000.99

c: checking: $100.99

---

a: joint: $0.00

b: saving: $10000.99

c: checking: $100.99

---

a: saving: $10101.98

b: saving: $10101.98

c: checking: $100.99

---

a: saving: $10302.98

b: saving: $10302.98

c: checking: $201.00

---

for reason "joint" balance comes 0 , unsure why. should show $10101.98

the main:

#include <iostream> #include "account.h" using namespace std; void displayabc(const account& a,     const account& b,     const account& c) {     cout << "a: " << << endl << "b: " << b << endl             << "c: " << c << endl << "--------" << endl; } int main() {     account a;     account b("saving", 10000.99);     account c("checking", 100.99);     displayabc(a, b, c);     = b + c;     displayabc(a, b, c);     = "joint";     displayabc(a, b, c);     = b += c;     displayabc(a, b, c);     = b += c += 100.01;     displayabc(a, b, c);     return 0; } 

source file:

#include <iomanip> #include <cstring> #include "account.h" using namespace std;      account::account() {             name_[0] = 0;             balance_ = 0;     }     account::account(double balance) {             name_[0] = 0;             balance_ = balance;     }     account::account(const char name[], double balance) {             strncpy(name_, name, 40);             name_[40] = 0;             balance_ = balance;     }       void account::display(bool gotonewline)const {             cout << (name_[0] ? name_ : "no name") << ": $" << setprecision(2) << fixed << balance_;             if (gotonewline) cout << endl;     }      account& account::operator+=(account& other) {              balance_ += other.balance_;             return *this;     }      account& account::operator=(const account& ls) {                      strcpy(name_, ls.name_);              balance_ = ls.balance_;              return *this;      }      account operator+(const account &one, const account &two) {             return account(one.balance_ + two.balance_);     }      ostream& operator<<(ostream& os, const account& a) {             a.display();             return os;     } 

header file:

#ifndef _account_h__ #define _account_h__ #include <iostream>      class account {             char name_[41];             double balance_;     public:             account();             account(double balance);             account(const char name[], double balance = 0.0);             void display(bool gotonewline = true)const;              account& operator+=(account& other);             account& operator=(const account & other);             friend account operator+(const account &one, const account    &two);          };      std::ostream& operator<<(std::ostream& os, const account& a); };  #endif 

change += operator method to:

account& operator+=(const account& other);