#! /usr/bin/env python3
#
def lambda_value ( lambda_input = None ):

#*****************************************************************************80
#
## lambda_value() allows the user to work with a global variable lambda.
#
#  Discussion:
#
#    Don't actually call the variable "lambda" because that's a Python keyword!
#
#  Modified:
#
#    02 October 2021
#
#  Author:
#
#    John Burkardt
#
  if not hasattr ( lambda_value, "lambda_default" ):
    lambda_value.lambda_default = 4.0

  if ( lambda_input is not None ):
    lambda_value.lambda_default = lambda_input

  lambda_output = lambda_value.lambda_default

  return lambda_output

def lambda_value_test ( ):

  print ( "lambda_value_test:" )
  
  lambda_output = lambda_value ( )
  print ( "" )
  print ( "  Calling with no arguments returns the default:" )
  print ( "    lambda_output = lambda_value ( ) = ", lambda_output )

  lambda_value ( 99.0 )
  print ( "" )
  print ( "  Calling with an argument resets the default:" )
  print ( "    lambda_value ( 99.0 )" )

  lambda_output = lambda_value ( )
  print ( "" )
  print ( "  Calling with no arguments returns the (new) default:" )
  print ( "    lambda_output = lambda_value ( ) = ", lambda_output )

  lambda_output = lambda_value ( 33.0 )
  print ( "" )
  print ( "  Calling with input and output returns the new default:" )
  print ( "    lambda_output = lambda_value ( 33 ) = ", lambda_output )

if ( __name__ == '__main__' ):
  lambda_value_test ( )