#! /usr/bin/env python
#
def disk_grid_regular ( n, r, c, ng ):

#*****************************************************************************80
#
## DISK_GRID_REGULAR computes grid points inside a disk.
#
#  Discussion:
#
#    The grid is defined by specifying the radius and center of the disk,
#    and the number of subintervals N into which the horizontal radius
#    should be divided.  Thus, a value of N = 2 will result in 5 points
#    along that horizontal line.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    07 April 2015
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer N, the number of subintervals.
#
#    Input, real R, the radius of the disk.
#
#    Input, real C(2), the coordinates of the center of the disk.
#
#    Input, integer NG, the number of grid points, as determined by
#    DISK_GRID_COUNT.
#
#    Output, real CG(2,NG), the grid points inside the disk.
#
  import numpy as np

  cg = np.zeros ( [ 2, ng ] )

  p = 0

  for j in range ( 0, n + 1 ):

    i = 0
    x = c[0]
    y = c[1] + r * float ( 2 * j ) / float ( 2 * n + 1 )
    cg[0,p] = x
    cg[1,p] = y
    p = p + 1

    if ( 0 < j ):

      cg[0,p] = x
      cg[1,p] = 2.0 * c[1] - y
      p = p + 1

    while ( True ):

      i = i + 1
      x = c[0] + r * float ( 2 * i ) / float ( 2 * n + 1 )
      if ( r * r < ( x - c[0] ) ** 2 + ( y - c[1] ) ** 2 ):
        break

      cg[0,p] = x
      cg[1,p] = y
      p = p + 1
      cg[0,p] = 2.0 * c[0] - x
      cg[1,p] = y
      p = p + 1

      if ( 0 < j ):
        cg[0,p] = x
        cg[1,p] = 2.0 * c[1] - y
        p = p + 1;
        cg[0,p] = 2.0 * c[0] - x
        cg[1,p] = 2.0 * c[1] - y
        p = p + 1

  return cg

def disk_grid_regular_test ( ):

#*****************************************************************************80
#
#% DISK_GRID_REGULAR_TEST tests DISK_GRID_REGULAR.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    07 April 2015
#
#  Author:
#
#    John Burkardt
#
  import numpy as np
  import platform

  from disk_grid_regular_count import disk_grid_regular_count
  from disk_grid_display import disk_grid_display
  from r82vec_print_part import r82vec_print_part
  from r8mat_transpose_write import r8mat_transpose_write

  print ( '' )
  print ( 'DISK_GRID_REGULAR_TEST:' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  DISK_GRID_REGULAR can define a grid of points' )
  print ( '  with N+1 points on a horizontal or vertical radius,' )
  print ( '  based on any disk.' )

  n = 20
  r = 2.0
  c = np.array ( [ 1.0, 5.0 ] )

  print ( '' )
  print ( '  We use N = %d' % ( n ) )
  print ( '  Radius R = %g' % ( r ) )
  print ( '  Center C = (%g,%g)' % ( c[0], c[1] ) )

  ng = disk_grid_regular_count ( n, r, c )

  print ( '' )
  print ( '  Number of grid points will be %d' % ( ng ) )

  cg = disk_grid_regular ( n, r, c, ng )

  r82vec_print_part ( ng, cg, 20, '  Part of the grid point array:' )
#
#  Write grid points to a file.
#
  filename = 'disk_grid_regular.xy'

  r8mat_transpose_write ( filename, 2, ng, cg )

  print ( '' )
  print ( '  Data written to the file "%s".' % ( filename ) )
#
#  Plot the grid, and save the plot in a file.
#
  filename = 'disk_grid_regular.png'
  disk_grid_display ( n, r, c, ng, cg, filename )
#
#  Terminate.
#
  print ( '' )
  print ( 'DISK_GRID_REGULAR_TEST:' )
  print ( '  Normal end of execution.' )
  return
  
if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  disk_grid_regular_test ( )
  timestamp ( )