Question

1. Write a recursive procedure called instanceCount that counts the number of instances of a number in a list

(instanceCount '(1 2 3 4 3 2 1) 3) => 2

2. Write a recursive procedure called excludeElement that receives a list and a number. It returns a new list with all instances of that number removed

(excludeElement '(1 2 3 4 3 2 1) 3) => (1 2 4 2 1)

Answer 1

1)

Write a recursive procedure called instanceCount that counts the number of instances of a number in a list

(instanceCount '(1 2 3 4 3 2 1) 3) => 2

lisp code:

(defun instanceCount (l n)
; declaring variable c with value 0
(setq c 0)
; for loop for item in list
(loop for i in l
; condition for checking equal
do(if(= i n)
; condition true the c value incremenet
(incf c 1)))
(write c)
)

(instanceCount '(1 2 3 4 3 2 1) '3)

output:

2

2). Write a recursive procedure called excludeElement that receives a list and a number. It returns a new list with all instances of that number removed

(excludeElement '(1 2 3 4 3 2 1) 3) => (1 2 4 2 1)

lisp code:

(defun excludeElement (l n)
; creating list
(setq mynewlist '())
; for llop for given list
(loop for x in l
; condition check if item not equal to given num then append to new list
do(setq mynewlist (append mynewlist (if (/= x n) (list x))))
)
; printng new list
(write mynewlist)
)

(excludeElement '(1 2 3 4 3 2 1) '3)

ouput:

(1 2 4 2 1)

Note:

• ; indicates comment for code line