Complex numbers in

Question

I'm studing structures, in the fallowing code my teacher created a structure of the complex numbers (numbers that are formed by two parts: a real one and an imaginary one).

#include <iostream>
#include <cmath>
#ifndef COMPLEX_DATA_H
#define COMPLEX_DATA_H
struct complex_data 

 {
   double re = 0; // real part
   double im = 0; // immaginary part
 };

#endif

int main()

 {

  std::cout << "Insert two complex numbers (re, im): ";
  complex_data z1, z2;
  std::cin >> z1.re >> z1.im;
  std::cin >> z2.re >> z2.im;

  ... // the code continues

  }

I'd like to ask two questions:

1. Leaving z1 and z2 uninitialized will cause any trouble considering they're inside a function and their default inizialitation is undefined?

2. How can we write the actual form of a variable that is a complex number?

   In reality is something like this c = 3 + 2i.

   But if we write it, the computer will sum it because it don't know the difference between real numbers and imaginary ones. So we'll be forced to use a string, but in this case it'll become a sequence of charcaters! Any idea?

   Using Ubuntu 14.04, g++ 4.9.2.

Answer 1

Since C++11, you have User defined literal (and since C++14 you have the standard literal operator ""i for the pure imaginary number of std::complex<double>).

You may write your own operator ""_i for your custom struct complex_data and also operator + to have what you expect, something like:

constexpr complex_data operator"" _i(unsigned long long d)
{ return complex_data{ 0.0, static_cast<double>(d) }; }

Live example.

Answer 2

Q1- Constructors are meant to intialize the member variables use them. Q2- Actual Form can be written using strings its just matter of displaying. c = 3 + 2i. Compiler really dont know this, you can overload + operarator. if you define + operator addition will be performed. (whatever code is written in that function e.g real+= a.real;)