Code using LISP.

Create a recursive function ALPHABET that takes a list of letters. It returns a list of the same length with the corresponding integer substituted for the letter (A becomes 1). Do error checking on the input. Return the empty list if the list is empty. You may use a global parameter to store letter-integer pairs.

Example input and output:

[42]> (alphabet '(a b z))

(1 2 26)

[43]> (alphabet '())

NIL

[44]> (alphabet "foo")

Error in ALPHABET function. The parameter must be a list. It was given "foo."

NIL