Notes on HW from Section 2.2

• Exercise 2.2.8 suggests you review your function digitCount from Ex 1.12.3. This is a little misleading since although there are similarities, there are important differences between the problems as well. In particular, although digitCount(0) should return 1 (since 0 has one digit, itself), digify(0) should return [] (empty list)... since that makes the rest of the problem easier. Bonus hint: use not only div (as in digitCount) to remove the least significant digit, but use also mod to retreive that digit.
• For Exercise 2.2.9, the hint is suggesting you set up the problem this way:

fun cat([], yy) = ??
  | cat(x::rest, yy) = ??