#  _________________________________________________________________________
#
#  PyUtilib: A Python utility library.
#  Copyright (c) 2008 Sandia Corporation.
#  This software is distributed under the BSD License.
#  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
#  the U.S. Government retains certain rights in this software.
#  _________________________________________________________________________

__all__ = ['infinity', 'nan', 'is_nan', 'is_finite']

"""
Definitions of mathematical constants
"""

import sys
import math


if sys.version_info < (2,6):
    """ Definition of infinity """
    infinity = float(1e3000)

    """ Definition of NaN """
    nan = infinity/infinity

    def is_nan(x):
        """
        Returns true if the argument is a float and it does not equal itself
        """
        return type(x) is float and x != x
    
    def is_finite(val):
        """
        Returns true if the argument is a float or int and it is not infinite or NaN
        """
        return type(val) in (float,int) and val not in (infinity, -infinity, nan)

else:
    """ Definition of infinity """
    infinity = float('inf')

    """ Definition of NaN """
    nan = infinity/infinity


    def is_nan(x):
        """
        Returns true if the argument is a float and it does not equal itself
        """
        try:
            return math.isnan(x)
        except TypeError:
            return False
    
    def is_finite(x):
        """
        Returns true if the argument is a float or int and it is not infinite or NaN
        """
        try:
            return not math.isinf(x)
        except TypeError:
            return False

