import string


def convert_digit_to_decimal(digit):
    """Compute the base-10 representation of a digit from a non-base 10 number.

       Parameters:
       digit: str -- can be any symbol used to represent a digit in a number,
                     base 2-36

       Return: float -- the decimal representation of the value of digit
    """
    # list of all English letters
    alpha = list(string.ascii_lowercase)
    # if digit a letter
    if digit in alpha:
        for i in range(len(alpha)):
            if digit.lower() == alpha[i]:
                # return the sum of 10, and the index of the letter in alphabet
                return 10 + i
    # if the number is 0-9, it's decimnal representation is no different
    else:
        return float(digit)