14.5. Output¶

As usual when we define a new class, we want to be able to output objects in a human-readable form. For Complex objects, we could use two functions:

void Complex::printCartesian ()
{
  cout << getReal() << " + " << getImag() << "i" << endl;
}

void Complex::printPolar ()
{
  cout << getMag() << " e^ " << getTheta() << "i" << endl;
}

The nice thing here is that we can output any Complex object in either format without having to worry about the representation. Since the output functions use the accessor functions, the program will compute automatically any values that are needed.

The following code creates a Complex object using the second constructor. Initially, it is in Cartesian format only. When we invoke printCartesian it accesses real and imag without having to do any conversions.

Complex c1 (2.0, 3.0);

c1.printCartesian();
c1.printPolar();

When we invoke printPolar, and printPolar invokes getMag, the program is forced to convert to polar coordinates and store the results in the instance variables. The good news is that we only have to do the conversion once. When printPolar invokes getTheta, it will see that the polar coordinates are valid and return theta immediately.

The output of this code is:

2 + 3i
3.60555 e^ 0.982794i

The active code below uses the print functions for Complex objects. Feel free to modify the code and experiment around!

#include <iostream>
#include <cmath>
using namespace std;

class Complex
{
  double real, imag;
  double mag, theta;
  bool cartesian, polar;

public:
  Complex ();
  Complex (double r, double i);
  void calculateCartesian ();
  double getReal ();
  double getImag ();
  void calculatePolar ();
  double getMag ();
  double getTheta ();
  void printCartesian ();
  void printPolar ();
};

int main() {
  Complex c1 (2.0, 3.0);
  c1.printCartesian();
  c1.printPolar();
}
====
Complex::Complex () { cartesian = false;  polar = false; }

Complex::Complex (double r, double i) {
  real = r;  imag = i;
  cartesian = true;  polar = false;
}

void Complex::calculateCartesian () {
  real = mag * cos (theta);
  imag = mag * sin (theta);
  cartesian = true;
}

double Complex::getReal () {
  if (cartesian == false) calculateCartesian ();
  return real;
}

double Complex::getImag () {
  if (cartesian == false) calculateCartesian ();
  return imag;
}

void Complex::calculatePolar () {
  mag = sqrt(pow(real, 2) + pow(imag, 2));
  theta = atan(imag / real);
  polar = true;
}

double Complex::getMag () {
  if (polar == false) {
    calculatePolar ();
  }
  return mag;
}

double Complex::getTheta () {
  if (polar == false) {
    calculatePolar ();
  }
  return theta;
}

void Complex::printCartesian () {
  cout << getReal() << " + " << getImag() << "i" << endl;
}

void Complex::printPolar () {
  cout << getMag() << " e^ " << getTheta() << "i" << endl;
}

Q-2: What is the correct output of the code below?

int main() {
  Complex c1 (3.0, 4.0);
  // c1.printCartesian();
  c1.printPolar();
}

5 e^ 0.927295i
Correct!
3 + 4i
Incorrect! Try using the active code above.
2 + 3i
Incorrect! Try using the active code above.
5 e^ 1
Incorrect! Try using the active code above.

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