q3.cpp

#include <iostream>
#include <cmath>

using namespace std;

class QuadraticCalculator {
  public:

    string numberOfSolutions();
    void printSolutions();

    QuadraticCalculator(double, double, double);

  private:

    /* Quotients */
    double a;
    double b;
    double c;

    double discriminant();
    bool hasInfinitySolutions();
    bool hasNoSolution();
    bool hasNoRealSolution();
    bool hasOneSolution();
    bool hasTwoSolutions();
};

QuadraticCalculator::QuadraticCalculator(double varA, double varB, double varC) {
  a = varA;
  b = varB;
  c = varC;
}

double QuadraticCalculator::discriminant() {
  return (b*b) - (4*(a*c));
}

bool QuadraticCalculator::hasInfinitySolutions() {
  return (a == 0) && (b == 0) && (c == 0);
}

bool QuadraticCalculator::hasNoSolution() {
  return (a == 0) && (b == 0) && (c != 0);
}

bool QuadraticCalculator::hasNoRealSolution() {
  return (discriminant() < 0);
}

bool QuadraticCalculator::hasOneSolution() {
  return (discriminant() == 0);
}

bool QuadraticCalculator::hasTwoSolutions() {
  return (discriminant() > 0);
}

string QuadraticCalculator::numberOfSolutions() {
  const string INFINITE_SOLUTIONS = "an infinite number of solutions";
  const string NO_SOLUTION        = "no solution";
  const string NO_REAL_SOLUTION   = "no real solution";
  const string ONE_SOLUTION       = "a single real solution";
  const string TWO_SOLUTIONS      = "two real solutions";

  string result;

  if (hasInfinitySolutions()) {
    result = INFINITE_SOLUTIONS; 
  } else if (hasNoSolution()) {
    result = NO_SOLUTION;
  } else if (hasNoRealSolution()) {
    result = NO_REAL_SOLUTION;
  } else if (hasOneSolution()) {
    result = ONE_SOLUTION;
  } else if (hasTwoSolutions()) {
    result = TWO_SOLUTIONS;
  }

  return result;
}

void QuadraticCalculator::printSolutions() {
  double x1;
  double x2;

  if (hasNoSolution() || hasInfinitySolutions() || hasNoRealSolution()) {
    cout << endl;
  } else {
    if (hasTwoSolutions()) {
      x1 = (-b + sqrt(discriminant())) / 2*a;
      x2 = (-b - sqrt(discriminant())) / 2*a;

      cout << " x1=" << x1 << " and " << "x2=" << x2 << endl;
    } else if (hasOneSolution()) {
      x1 = -b / 2*a;

      cout << " x=" << x1 << endl;
    }
  }
}

int main() {
  double a;
  double b;
  double c;

  cout << "Please enter value of a: ";
  cin  >> a;
  cout << "Please enter value of b: ";
  cin  >> b;
  cout << "Please enter value of c: ";
  cin  >> c;

  QuadraticCalculator calc(a, b, c);

  cout << "The equation has " << calc.numberOfSolutions();
  calc.printSolutions();

  return 0;
}