''' Purpose: better experience functional development
'''

# helpful named strings

# If you write functions in the same module, you can call those functions defined in the
# same file in other functions without importing the module and doing module.function_name()
# We don't have to import quad in quad.py! We're already in quad!
# So if you want to use the lower( strings ) function in the same
# module (quad.py like in canoncial()) just call lower( strings ) no need to do
# quad.lower( strings ) in the same file!

PUNCTUATION = '''!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~'''
WHITE_SPACE = ' \t\n\r\v\f'
EXTRANEOUS  = PUNCTUATION + WHITE_SPACE

def lower( strings ) :
    ''' Returns a new list whose elements are lower case versions of
        those in strings
    '''
    result = [] # accumulator - build up a list of the lowercase strings
    # You can call .lower() on a single string but a list doesn't have a lower function!
    for s in strings: # Go through each string in list of strings
        lowered_s = s.lower()    # Get the lowercase version
        result.append( lowered_s ) # Add the lowercase version to our result
    return result

def unique( strings ) :
    ''' Returns a new version of strings without any duplicate values
    '''

    pass

def strip( strings ) :
    ''' Returns a new version of strings where the corresponding
        elements have leading and trailing extraneous characters
        (punctuation or whitespace) removed
    '''

    pass

def canonical( strings ) :
    ''' Returns a new version of strings without duplicate values
        where the corresponding elements have leading and trailing
        extraneous characters (punctuation or whitespace) removed
        and are in lowercase
    '''
    # Do three things: remove extraneous characters, lowercase everything, and have
    # duplicate values removed ^ look at the above functions
    # Order matters! What order do we want to do these three things?

    # Call the functions above on the list of strings one by one!
    # Make all the strings lowercase!
    list_lowercase_strings = lower( strings )
    # Make all the lowercase strings stripped!
    list_stripped_lowercase_strings = strip( list_lowercase_strings )
    # Get rid of duplicates in the lowercase stripped versions! Remove duplicates last!
    list_stripped_lowercase_unique_strings = unique( list_stripped_lowercase_strings )

    return list_stripped_lowercase_unique_strings