A hexadecimal number notation represents the numbers 0–15. The traditional digits 0–9 are represented using standard digits. The numbers 10, 11, 12, 13, 14, and 15 are represented as using the characters a, b, c, d, e, and f, respectively. Using the notations discussed in this chapter, define a new inductive set, hexdigits, which models hexadecimal digits. Define a variant of the functions nextdigits and evendigit for this inductive set.