#! /usr/bin/env python
#
def laguerre_integral ( p ):

#*****************************************************************************80
#
## LAGUERRE_INTEGRAL evaluates a monomial integral associated with L(n,x).
#
#  Discussion:
#
#    The integral:
#
#      integral ( 0 <= x < +oo ) x^p * exp ( -x ) dx
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    14 January 2016
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Input, integer P, the exponent.
#    0 <= P.
#
#    Output, real S, the value of the integral.
#
  from r8_factorial import r8_factorial

  s = r8_factorial ( p )

  return s

def laguerre_integral_test ( ):

#*****************************************************************************80
#
## LAGUERRE_INTEGRAL_TEST tests LAGUERRE_INTEGRAL.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license. 
#
#  Modified:
#
#    14 January 2016
#
#  Author:
#
#    John Burkardt
#
  import platform

  print ( '' )
  print ( 'LAGUERRE_INTEGRAL_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  LAGUERRE_INTEGRAL returns Laguerre integrals of monomials:' )
  print ( '  M(k) = integral ( 0 <= x < +oo ) x^k exp(-x) dx' )
  print ( '' )
  print ( '     K            M(K)' )
  print ( '' )
  for k in range ( 0, 11 ):
    print ( '  %4d  %14.6g' % ( k, laguerre_integral ( k ) ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'LAGUERRE_INTEGRAL_TEST' )
  print ( '  Normal end of execution.' )
  return

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