Go back to Richel Bilderbeek's homepage.

Go back to Richel Bilderbeek's C++ page.

(C++) Exercise #6: refactoring quadratic solver

Difficulty: 2/10

Date added: 21th of July 2008

In this exercise you must refactor a class that is given as an example in reference [0] . You will learn how to think to correctly refactor a class and that literature does not always set a good examples.

A quadratic equation is an equation in the form 'ax² + bx + c = 0'. For which x or x's is this true? The number of solutions this equation has is determined by the discrimant: D = b² - 4ac. If D is smaller then zero, the equation has no solutions. If D equals zero, the solution to the equation is x = -b/2a. If D is bigger then zero, the solutions are x = (-b-sqrt(D)) / (2a) and x = (-b+sqrt(D)) / (2a).

Below of a piece of code (from [0] ) demonstrating a class to solve a quadratic equation. Can you refactor this class to follow good class design, method design, function design and good thinking?

#include <cmath>

using namespace std;

class Qs

{

public:

void coeff(double aa, double bb, double cc)

{

a = aa;

b = bb;

c = cc;

}

bool solve()

{

double D = b * b - 4 * a * c;

if (a == 0 || D < 0) return false;

double rD = sqrt(D);

x1 = (-b + rD)/(2 * a);

x2 = (-b - rD)/(2 * a);

return true;

}

double root1() const { return x1; }

double root2() const { return x2; }

private:

double a,b,c,x1,x2;

};

View the answer of this exercise.

Post your feedback

Feel free to post your feedback about this exercise at Programmer's Heaven.

References

[0]          Leen Ammeraal. C++ (6th edition). ISBN: 90-395-1935-8. 2001.

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.