#! /usr/bin/env python
#
def p_integral ( n ):

#*****************************************************************************80
#
## P_INTEGRAL evaluates a monomial integral associated with P(n,x).
#
#  Discussion:
#
#    The integral:
#
#      integral ( -1 <= x < +1 ) x^n dx
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    15 March 2016
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer N, the exponent.
#    0 <= N.
#
#    Output, real VALUE, the value of the integral.
#
  if ( ( n % 2 ) == 1 ):
    value = 0.0
  else:
    value = 2.0 / ( n + 1 )

  return value

def p_integral_test ( ):

#*****************************************************************************80
#
## P_INTEGRAL_TEST tests P_INTEGRAL.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license. 
#
#  Modified:
#
#    15 March 2016
#
#  Author:
#
#    John Burkardt
#
  import platform

  print ( '' )
  print ( 'P_INTEGRAL_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  P_INTEGRAL returns the integral of P(n,x) over [-1,+1].' )
  print ( '' )
  print ( '     N                  Integral' )
  print ( '' )

  for n in range ( 0, 11 ):

    value = p_integral ( n )

    print ( '  %4d  %24.16g' % ( n, value ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'P_INTEGRAL_TEST' )
  print ( '  Normal end of execution.' )
  return

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