#! /usr/bin/env python
#
def r8_epsilon ( ):

#*****************************************************************************80
#
## R8_EPSILON returns the R8 roundoff unit.
#
#  Discussion:
#
#    The roundoff unit is a number R which is a power of 2 with the 
#    property that, to the precision of the computer's arithmetic,
#      1 < 1 + R
#    but 
#      1 = ( 1 + R / 2 )
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    03 June 2013
#
#  Author:
#
#    John Burkardt
#
#  Parameters:
#
#    Output, real VALUE, the roundoff unit.
#
  value = 2.220446049250313E-016

  return value

def r8_epsilon_test ( ):

#*****************************************************************************80
#
## R8_EPSILON_TEST tests R8_EPSILON.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    01 September 2012
#
#  Author:
#
#    John Burkardt
#
  import platform

  print ( '' )
  print ( 'R8_EPSILON_TEST' )
  print ( '  Python version: %s' % ( platform.python_version ( ) ) )
  print ( '  R8_EPSILON produces the R8 roundoff unit.' )
  print ( '' )

  r = r8_epsilon ( )
  print ( '  R = R8_EPSILON()         = %e' % ( r ) )

  s = ( 1.0 + r ) - 1.0
  print ( '  ( 1 + R ) - 1            = %e' % ( s ) )

  s = ( 1.0 + ( r / 2.0 ) ) - 1.0
  print ( '  ( 1 + (R/2) ) - 1        = %e' % ( s ) )
#
#  Terminate.
#
  print ( '' )
  print ( 'R8_EPSILON_TEST' )
  print ( '  Normal end of execution.' )
  return

if ( __name__ == '__main__' ):
  from timestamp import timestamp
  timestamp ( ) 
  r8_epsilon_test ( )
  timestamp ( )