function_pointer_array_new.cpp

# include <cstdlib>
# include <iostream>
# include <iomanip>
# include <ctime>

using std::cerr;
using std::cout;
using std::setw;

int main ( int argc, char *argv[] );
double r8_ave ( double x, double y );
double r8_max ( double x, double y );
double r8_min ( double x, double y );
double r8_sum ( double x, double y );
double r8_uniform_01 ( int *seed );
void timestamp ( );

typedef double ( *FPType ) ( double x, double y );

//****************************************************************************80

int main ( int argc, char *argv[] )

//****************************************************************************80
//
//  Purpose:
//
//    MAIN is the main program for the FUNCTION POINTER ARRAY NEW demonstration.
//
//  Discussion:
//
//    This is an example of how to declare and use an array of function 
//    pointers whose dimension is not initially specified, so that the 
//    number of entries can be chosen when allocating space with the NEW
//    command.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    20 April 2009
//
//  Author:
//
//    John Burkardt
//
{
  double a;
  double b;
  double c;
  double d;
  int dim;
  int dim_num;
  double e;
  FPType *func;
  int i;
  int seed;
  
  timestamp ( );
  cout << "\n";
  cout << "FUNCTION_POINTER_ARRAY_NEW\n";
  cout << "  C++ version\n";
  cout << "\n";
  cout << "  Example of a dynamically dimensioned function pointer array.\n";
  cout << "\n";
  cout << "  We define an array FUNC whose entries are function pointers.\n";
  cout << "  Our declaration indicates only that each entry of FUNC \n";
  cout << "  points to a function which has two inputs of type double,\n";
  cout << "  and returns a double as its value.\n";
  cout << "\n";
  cout << "  We create and delete versions of this array dynamically.\n";
  cout << "  using sizes of 2 and 4.\n";

  seed = 12345689;

  dim_num = 2;
  func = new FPType[dim_num];
  func[0] = r8_min;
  func[1] = r8_max;

  cout << "\n";
  cout << "  Set DIM_NUM = " << dim_num << "\n";
  cout << "  Set FUNC = { r8_min ( ), r8_max ( ) }";
  cout << "\n";
  cout << "  -----A----  -----B----     FUNC[0]     FUNC[1]\n";
  cout << "                            min(A,B)    max(A,B)\n";
  cout << "\n";

  for ( i = 0; i < 5; i++ )
  {
    a = r8_uniform_01 ( &seed );
    cout << "  " << setw(10) << a;
    b = r8_uniform_01 ( &seed );
    cout << "  " << setw(10) << b;
    for ( dim = 0; dim < dim_num; dim++ )
    {
      cout << "  " << setw(10) << func[dim] ( a, b );
    }
    cout << "\n";
  }

  delete [] func;

  seed = 12345689;

  dim_num = 4;
  func = new FPType[dim_num];
  func[0] = r8_max;
  func[1] = r8_ave;
  func[2] = r8_min;
  func[3] = r8_sum;

  cout << "\n";
  cout << "  Set DIM_NUM = " << dim_num << "\n";
  cout << "  Set FUNC = { r8_min ( ), r8_max ( ) }";
  cout << "\n";
  cout << "  -----A----  -----B----     FUNC[0]     FUNC[1]     FUNC[2]     FUNC[3]\n";
  cout << "                            max(A,B)    ave(A,B)    min(A,B)    sum(A,B)\n";
  cout << "\n";

  for ( i = 0; i < 5; i++ )
  {
    a = r8_uniform_01 ( &seed );
    cout << "  " << setw(10) << a;
    b = r8_uniform_01 ( &seed );
    cout << "  " << setw(10) << b;
    for ( dim = 0; dim < dim_num; dim++ )
    {
      cout << "  " << setw(10) << func[dim] ( a, b );
    }
    cout << "\n";
  }

  delete [] func;
//
//  Terminate.
//
  cout << "\n";
  cout << "FUNCTION_PONTER_ARRAY_NEW:\n";
  cout << "  Normal end of execution.\n";

  cout << "\n";
  timestamp ( );

  return 0;
}
//****************************************************************************80

double r8_ave ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_AVE returns the average of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    28 March 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_AVE, the average of X and Y.
//
{
  double value;

  value = ( x + y ) / 2.0;

  return value;
}
//****************************************************************************80

double r8_max ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_MAX returns the maximum of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    18 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_MAX, the maximum of X and Y.
//
{
  double value;

  if ( y < x )
  {
    value = x;
  } 
  else
  {
    value = y;
  }
  return value;
}
//****************************************************************************80

double r8_min ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_MIN returns the minimum of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    31 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_MIN, the minimum of X and Y.
//
{
  double value;

  if ( y < x )
  {
    value = y;
  } 
  else
  {
    value = x;
  }
  return value;
}
//****************************************************************************80

double r8_sum ( double x, double y )

//****************************************************************************80
//
//  Purpose:
//
//    R8_SUM returns the sum of two R8's.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    13 March 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, double X, Y, the quantities to compare.
//
//    Output, double R8_SUM, the sum of X and Y.
//
{
  double value;

  value = x + y;

  return value;
}
//****************************************************************************80

double r8_uniform_01 ( int *seed )

//****************************************************************************80
//
//  Purpose:
//
//    R8_UNIFORM_01 returns a unit pseudorandom R8.
//
//  Discussion:
//
//    This routine implements the recursion
//
//      seed = ( 16807 * seed ) mod ( 2^31 - 1 )
//      u = seed / ( 2^31 - 1 )
//
//    The integer arithmetic never requires more than 32 bits,
//    including a sign bit.
//
//    If the initial seed is 12345, then the first three computations are
//
//      Input     Output      R8_UNIFORM_01
//      SEED      SEED
//
//         12345   207482415  0.096616
//     207482415  1790989824  0.833995
//    1790989824  2035175616  0.947702
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    11 August 2004
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    Paul Bratley, Bennett Fox, Linus Schrage,
//    A Guide to Simulation,
//    Second Edition,
//    Springer, 1987,
//    ISBN: 0387964673,
//    LC: QA76.9.C65.B73.
//
//    Bennett Fox,
//    Algorithm 647:
//    Implementation and Relative Efficiency of Quasirandom
//    Sequence Generators,
//    ACM Transactions on Mathematical Software,
//    Volume 12, Number 4, December 1986, pages 362-376.
//
//    Pierre L'Ecuyer,
//    Random Number Generation,
//    in Handbook of Simulation,
//    edited by Jerry Banks,
//    Wiley, 1998,
//    ISBN: 0471134031,
//    LC: T57.62.H37.
//
//    Peter Lewis, Allen Goodman, James Miller,
//    A Pseudo-Random Number Generator for the System/360,
//    IBM Systems Journal,
//    Volume 8, Number 2, 1969, pages 136-143.
//
//  Parameters:
//
//    Input/output, int *SEED, the "seed" value.  Normally, this
//    value should not be 0.  On output, SEED has been updated.
//
//    Output, double R8_UNIFORM_01, a new pseudorandom variate, 
//    strictly between 0 and 1.
//
{
  int i4_huge = 2147483647;
  int k;
  double r;

  if ( *seed == 0 )
  {
    cerr << "\n";
    cerr << "R8_UNIFORM_01 - Fatal error!\n";
    cerr << "  Input value of SEED = 0.\n";
    exit ( 1 );
  }

  k = *seed / 127773;

  *seed = 16807 * ( *seed - k * 127773 ) - k * 2836;

  if ( *seed < 0 )
  {
    *seed = *seed + i4_huge;
  }
//
//  Although SEED can be represented exactly as a 32 bit integer,
//  it generally cannot be represented exactly as a 32 bit real number.
//
  r = ( double ) ( *seed ) * 4.656612875E-10;

  return r;
}
//****************************************************************************80

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    TIMESTAMP prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    May 31 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    03 October 2003
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    None
//
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct tm *tm;
  size_t len;
  time_t now;

  now = time ( NULL );
  tm = localtime ( &now );

  len = strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm );

  cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}