Question

Lisp program

count-of (symbol list): Write a function named count-of that takes two parameters, a symbol and a list. Count the number of instances of x in the list. Do not count the number of x in any sub-lists within the list.

Test: count-of 'a '(a 'a(a c) d c a).

Result: 2

trim-to (symbol list): Write a function named trim-to that takes a symbol and list as parameters. Return a new list starting from the first occurrence of the input symbol in the input list. If there is no occurrence of the symbol, return nil.

Test: trim-to 'c '(a b c d e)

Result: (C D E)

Answer 1

(defun count-of (symbol l)
(if (null l)
0
(if (equal (car l) symbol)
(+ 1 (count-of symbol (cdr l)))
(count-of symbol (cdr l))
)
)
)

(defun trim-of(symbol l)
(if (null l)
l
(if (equal (car l) symbol)
l
(trim-of symbol (cdr l))
)
)
)