Question

I am a C++ beginner. I have the following code, the reult is not what I expect. The question is why, resp. what is wrong. For sure, the most of you see it at the first glance.

struct Complex {
    float imag;
    float real;
    Complex( float i, float r) {
        imag = i;
        real = r;
    }
    Complex( float r) {
        Complex(0, r);
    }
    std::string str() {
        std::ostringstream s;
        s << "imag: " << imag << " | real: " << real << std::endl;
        return s.str();
    }
};
class Complexes {
    std::vector<Complex> * _complexes;
public:
    Complexes(){
        _complexes = new std::vector<Complex>;
    }
    void Add( Complex elem ) {
        _complexes->push_back( elem ); 
    }
    std::string str( int index ) {
        std::ostringstream oss;
        Complex c = _complexes->at(index);
        oss << c.str();
        return oss.str();
    }
};
int main(){
    Complexes * cs = new Complexes();
    //cs->Add(123.4f);
    cs->Add(Complex(123.4f));
    std::cout << cs->str(0); return 0; }

for now I am interested in the basics of c++ not in the complexnumber theory 😉
it would be nice if the “Add” function does also accept one real (without an extra overloading) instead of only a Complex-object is this possible?

many thanks in advance
Oops

Answer 1

You can’t call one constructor in the body of another one like that:

Complex( float r) {
        Complex(0, r);
    }

In C++ it creates a temporary object of class Complex which immediately gets destroyed.

You could use default parameters in the constructor or some private method that would be called by constructors