#! /usr/bin/env python3
#
def random_permutation ( n, x, seed ):

#****************************************************************************80
#
#  Purpose:
#
#    RANDOM_PERMUTATION applies a random permutation to an array.
#
#  Modified:
#
#    19 February 2016
#
#  Author:
#
#    Original C version by Warren Smith.
#    Python version by John Burkardt.
#
#  Parameters:
#
#    Input, integer N, indicates the size of X.
#
#    Input/output, double X[N+2].  On output, entries X[1] through
#    X[N] have been randomly permuted.
#
#    Input/output, integer SEED, a seed for the random number generator.
#
  from i4_uniform_ab import i4_uniform_ab

  for i in range ( 1, n + 1 ):

    j, seed = i4_uniform_ab ( i, n, seed )

    t    = x[i]
    x[i] = x[j]
    x[j] = t      
  
  return x

def random_permutation_test ( ):

#*****************************************************************************80
#
## RANDOM_PERMUTATION_TEST tests RANDOM_PERMUTATION.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    19 February 2016
#
#  Author:
#
#    John Burkardt
#
  import platform
  from r8vec_indicator0 import r8vec_indicator0
  from r8vec_print import r8vec_print

  print ( '' )
  print ( 'RANDOM_PERMUTATION_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  RANDOM_PERMUTATION randomly permutes entries 1 through N of' )
  print ( '  a vector X[0:N+1].' )

  n = 5
  x = r8vec_indicator0 ( n + 2 )
  seed = 123456789
  r8vec_print ( n + 2, x, '  Initial X:' )
  x = random_permutation ( n, x, seed )
  r8vec_print ( n + 2, x, '  Permuted X:' )
#
#  Terminate.
#
  print ( '' )
  print ( 'RANDOM_PERMUTATION_TEST' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( )
  random_permutation_test ( )
  timestamp ( )