9.7 Class Derivation Example

FILENAME: example6.cpp

Program:

/*

 * This example shows how a CosVec class may be derived
 * from the class RWMathVec<double>. Class CosVec objects are
 * double precision vectors that have been initialized
 * with cosines with a specified number of integral
 * cycles.
 */

// Include the RWMathVec<double> class header file:
#include <rw/math/mathvec.h>
#include <iostream.h>

/*
 * Start derived class declarations:
 * RWMathVec<double> is declared as a public base class 
 * for CosVec:
 */

class CosVec : public RWMathVec<double> {

public:

  // unadorned constructor:
  CosVec();

/* This is the useful constructor. We first use the
 * RWMathVec<double> constructor
 * RWMathVec<double>(n, val, by);
 * to create a vector of phases. Taking the cosine of 
 * this vector will yield the desired initial values for
 * the base class of CosVec.
 */
 
  CosVec (unsigned N, int cycles = 1) :
    ( cos(RWMathVec<double>(N,0,2*M_PI*cycles/N)) )
    { }

  // Copy constructor:
  CosVec (const CosVec& v) :
    (v)
    { }
};

main()
{
   /*
    * Initialize a CosVec object with 12 elements and one
    * cycle:
    */
   CosVec c(12,1);

   /*
    * Output the vector: note that class CosVec inherits
    * operator<< from the base class RWMathVec<double>.
    */

   cout << c;
}

Sample Input:

None required.

Sample Output (note that the exact numbers will depend on machine precision):

[
1 0.866025 0.5 0 -0.5
-0.866025 -1 -0.866025 -0.5 0
0.5 0.866025
]