# tempplus.py
# Walker M. White (wmw2)
# September 6, 2012
"""Conversion functions between fahrentheit and centrigrade

This module has been extended from the version in the previous
lecture to include script code that test the functions.
In addition, it shows the prefered way to construct an script:
using a testing function."""
import cornelltest

# Functions

def to_centigrade(x):
    """Returns: x converted to centigrade

    Value returned has type float.

    Precondition: x is a float measuring temperature in fahrenheit"""
    return 5*(x-32)/9.0

def to_fahrenheit(x):
    """Returns: x converted to fahrenheit

    Value returned has type float.

    Precondition: x is a float measuring temperature in centigrade"""
    return 9*x/5.0+32

# Constants

FREEZING_C = 0.0   # Temperature water freezes in centrigrade

FREEZING_F = to_fahrenheit(FREEZING_C)

BOILING_C = 100.0  # Temperature water freezes in centrigrade

BOILING_F = to_fahrenheit(BOILING_C)


# Test Procedure
def test_module():
    """Procedure to test out the conversion functions"""
    # Test to_centigrade
    cornelltest.assert_floats_equal(0.0,to_centigrade(32.0))
    cornelltest.assert_floats_equal(100.0,to_centigrade(212.0))
    cornelltest.assert_floats_equal(-40.0,to_centigrade(-40.0))

    # Test to_fahrenheit
    cornelltest.assert_floats_equal(32.0,to_fahrenheit(0.0))
    cornelltest.assert_floats_equal(212.0,to_fahrenheit(100.0))
    cornelltest.assert_floats_equal(-40.0,to_fahrenheit(-40.0))
    
    print 'The temperature module is working properly'
    
    
# Script code
if __name__ == '__main__':
    test_module()