import string


def tokenize_doc(doc):
    """
    Convert document to lowercase, remove punctuation, and split on whitespace

    :param doc: Document of text (list)
    :return: Tokens of document
    """
    
    doc = doc.lower()
    whitespace = string.whitespace + '\x03'  # End of file char
    trans = str.maketrans(whitespace, ' ' * len(whitespace), string.punctuation)
    doc_no_punc = doc.translate(trans)
    return doc_no_punc.split()