//	Ex722.cc

//	Sec. 7.2 of lecture
//		Function parameter by reference

#include <iostream.h>

//double sgn(double& x);		// by reference
double sgn(const double& x);		// by const. reference
double c_sgn(double& x);
//------------------------------------------

main()
{
 const double  a_const = 3.78;
 double a,b;
 
 cout << endl << " Input Argument      : ";
 cin  >> a;

 b  = sgn(a);		// by reference
 
 cout << " 1:  sgn(" << a << ") = " << b << endl;

 b  = sgn(a_const);	// by reference
 			//  works only with const. reference as parameter
 
 cout << " 2:  sgn(" << a_const << ") = " << b << endl;

 b  = c_sgn(a);		// by reference
 b  = sgn(4.5);		// by reference
 cout << "   sgn(Konst.) = " << b << endl;
 
}
//------------------------------------------
//		declare  function
//double sgn(double& x)				// reference
double sgn(const double& x)			// const. reference
{
  double y;
  
  if ( x > 0.0 ) 
    {
      y = 1.0 ;
    }
  else
    {
      if ( x == 0.0 )
	{
          y = 0.0 ;
	}
      else
	{
          y = -1.0 ;
	}
    } 
  return y;
}

//------------------------------------------

double c_sgn(double& x)
{
  return sgn(x);
}