toms112.cpp

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

using namespace std;

# include "toms112.hpp"

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

bool point_in_polygon ( int n, double x[], double y[], double x0, double y0 )

//****************************************************************************80
//
//  Purpose:
//
//    POINT_IN_POLYGON determines if a point is inside a polygon
//
//  Discussion:
//
//    If the points ( x(i), y(i) ) ( i = 1, 2, ..., n ) are,
//    in this cyclic order, the vertices of a simple closed polygon and
//    (x0,y0) is a point not on any side of the polygon, then the
//    procedure determines, by setting "point_in_polygon" to TRUE or FALSE,
//    whether (x0,y0) lies in the interior of the polygon.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license. 
//
//  Modified:
//
//    30 November 2016
//
//  Author:
//
//    John Burkardt
//
//  Reference:
//
//    Moshe Shimrat,
//    ACM Algorithm 112,
//    Position of Point Relative to Polygon,
//    Communications of the ACM,
//    Volume 5, Number 8, page 434, August 1962.
//
//    Richard Hacker,
//    Certification of Algorithm 112,
//    Communications of the ACM,
//    Volume 5, Number 12, page  606, December 1962.
//
//  Parameters:
//
//    Input, int N, the number of nodes or vertices in 
//    the polygon.  N must be at least 3.
//
//    Input, double X[N], Y[N], the vertices of the polygon.
//
//    Input, double X0, Y0, the coordinates of the point to be tested.
//
//    Output, bool POINT_IN_POLYGON, is TRUE if the point is
//    inside the polygon.
//
{
  int i;
  int ip1;
  double t;
  bool value;
  
  value = false;

  for ( i = 0; i < n; i++ )
  {
    ip1 = ( ( i + 1 ) % n );

    if ( ( y[ip1] < y0 ) == ( y0 <= y[i] ) )
    {
      t = x0 - x[i] - ( y0 - y[i] ) * ( x[ip1] - x[i] ) / ( y[ip1] - y[i] );
      if ( t < 0.0 )
      {
        value = ! value;
      }
    }
  }

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

void r8vec2_print ( int n, double a1[], double a2[], string title )

//****************************************************************************80
//
//  Purpose:
//
//    R8VEC2_PRINT prints an R8VEC2.
//
//  Discussion:
//
//    An R8VEC2 is a dataset consisting of N pairs of real values, stored
//    as two separate vectors A1 and A2.
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    19 November 2002
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    Input, int N, the number of components of the vector.
//
//    Input, double A1[N], double A2[N], the vectors to be printed.
//
//    Input, string TITLE, a title.
//
{
  int i;

  cout << "\n";
  cout << title << "\n";
  cout << "\n";
  for ( i = 0; i <= n - 1; i++ )
  {
    cout << setw(6)  << i
         << ": " << setw(14) << a1[i]
         << "  " << setw(14) << a2[i] << "\n";
  }

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

void timestamp ( )

//****************************************************************************80
//
//  Purpose:
//
//    TIMESTAMP prints the current YMDHMS date as a time stamp.
//
//  Example:
//
//    31 May 2001 09:45:54 AM
//
//  Licensing:
//
//    This code is distributed under the GNU LGPL license.
//
//  Modified:
//
//    08 July 2009
//
//  Author:
//
//    John Burkardt
//
//  Parameters:
//
//    None
//
{
# define TIME_SIZE 40

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

  now = std::time ( NULL );
  tm_ptr = std::localtime ( &now );

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

  std::cout << time_buffer << "\n";

  return;
# undef TIME_SIZE
}