Thread: quadratic root and imaginary result

Hello,

I have the following program, but the issue I'm having that whenever one of the roots is imaginary both solutions become zero. Any help with this will be appreciated.

Code:

#include <iostream>
#include <iomanip>

// this header file identifies all of the special mathematical functions.
#include <cmath>
using namespace std;

// Version 1.2 Adds functions for Quadratic roots of complex value
//    This is an incomplete version for students to work with
// Version 1.1 Removed standard method calls and implemented operator overloading
// Version 1.0 Initial complex value declaration

struct ComplexStruc {
   double real, imaginary;
} ;

class myComplex {
   double real, imaginary;
public:
   myComplex( double dReal = 0.0, double dImaginary = 0.0 );

   double getReal( void ) { return real; };
   double getImaginary( void ) { return imaginary; };
   void setReal( double dR ) { real = dR; };
   void setImaginary( double dI ) { imaginary = dI; };

   friend ostream& operator<<(ostream& osLeft, const myComplex& right);
   const myComplex operator +( const myComplex& right ) const;
   const myComplex operator -( const myComplex& right ) const;
   const myComplex operator *( const myComplex& right ) const;

} ;

double QuadraticRoot1( double dA, double dB, double dC )
{
   double dRoot = 0;
   double dIntermediate1 = 0.0, dIntermediate2 = 0.0;

   if( (dIntermediate1 = 4.0 * dA * dC) < (dIntermediate2 = dB * dB) ) {
      dRoot = (-dB - pow(dIntermediate2 - dIntermediate1, 0.5)) / (2.0 * dA);
   }
   else {
      // value is complex
   }
   return dRoot;
}

double QuadraticRoot2( double dA, double dB, double dC )
{
   double dRoot= 0;
   double dIntermediate1 = 0.0, dIntermediate2 = 0.0;

   if( (dIntermediate1 = 4.0 * dA * dC) < (dIntermediate2 = dB * dB) ) {
      dRoot = (-dB + pow(dIntermediate2 - dIntermediate1, 0.5)) / (2.0 * dA);
   }
   else {
      // value is complex
   }
   return dRoot;
}

int main()
{
   double dA, dB, dC ;

   myComplex mcA(1.2, 1.3), mcB(2.1, 2.3), mcC(0.0, 0.0);

   cout << endl << endl << endl << "Using overloaded operators" << endl << endl;

   cout << "The original value of parameter C is zero." << endl;
   cout << "Only the real component value of zero shows, " << mcC << endl << endl;

   mcC = (mcA + mcB);

   cout << "Addition, " << mcC << endl << endl ;
   cout << "Multiplication and subtraction (A*B)-B, " << (mcA*mcB)-mcB << endl << endl;

   do {
      cout << "Quadratic solution, input coefficients A, B then C "
         << endl << "enter all zeros to stop " << endl ;
      cin >> dA >> dB >> dC ;
      if( dA == 0 && dB == 0 && dC == 0 )
         break;
      cout << "Root 1 = " << QuadraticRoot1( dA, dB, dC ) << endl << endl ;
      cout << "Root 2 = " << QuadraticRoot2( dA, dB, dC ) << endl << endl ;
   } while( true );

   system( "pause" );
   return 0;
}

myComplex::myComplex(double dReal, double dImaginary)
{
   real = dReal;
   imaginary = dImaginary;
   return;
}

ostream& operator<<(ostream& osLeft, const myComplex& rhv)
{
   osLeft << fixed << setprecision(3) << rhv.real ;
   if( rhv.imaginary < 0 )
      osLeft << " - " ;
   else if( rhv.imaginary > 0 )
      osLeft << " + " ;
   else
      return osLeft;

   osLeft << abs(rhv.imaginary) << " j" ;

   return osLeft; 
}

const myComplex myComplex::operator +( const myComplex& rhv )const
{
   myComplex temp(0,0);
   temp.real = real + rhv.real;
   temp.imaginary = imaginary + rhv.imaginary;
   return temp;
}

const myComplex myComplex::operator -( const myComplex& rhv )const
{
   myComplex temp(0,0);
   temp.real = real - rhv.real;
   temp.imaginary = imaginary - rhv.imaginary;
   return temp;
}

const myComplex myComplex::operator *( const myComplex& rhv )const
{
   myComplex temp(0,0);
   temp.real = (real * rhv.real)  + (imaginary * rhv.imaginary);
   temp.imaginary = (real * rhv.imaginary)  + (imaginary * rhv.real);
   return temp;
}

This would probably be better suited for the C++ forum

Code:

double QuadraticRoot1( double dA, double dB, double dC )
{
    double dRoot = 0;

.
.
   else {
      // value is complex
   }
   return dRoot;

}


double QuadraticRoot2( double dA, double dB, double dC )
{
   double dRoot= 0;
   .
   . 
   else {
      // value is complex
   }
   return dRoot;
}

So,you have nothing in the else block therefore initial value of dRoot is returned.
ie. 0