Question

class test { public:     test &operator=(const test & other){} // 1     const test & operator+(const test& other) const {} // 2     const test & operator+(int m) {} //3 private:     int n; };  int main() { test t1 , t2, t3;  // this works fine  t1 = t2.operator+(t3) , calls  2 and 1 t1 = t2 + t3;   // this works fine    t1 = t2.operator+ (100). calls 3 and 1 t1 = t2 + 100;  //this works fine t1 = (t2.operator+ (100)).operator+ (t3) t1 = t2 + 100 +t3;  //why is the error in this one  ???? // it should be t1 = (t2.operator+ (t3)).operator+ (100) t1  =  t2 + t3 + 100;   return 0; } 

Answer 1

Because object returned by t2+t3 is const, and you cannot call its non-const function (3).

It works fine in case of ‘t1 = t2 + 100 +t3;’, because object returned by t2+100 is const too, but you are calling its const function (2), which is ok.