Write a Function 'total' that takes an orderd list ie.
((itemA quantityA costA)(itemB quantityB costB)....)
but returns a list giving the total cost plus the overall cost.
Eg:
LISP>(total'((book 2 10)(pen 3 2)(notepad 1 12)))
((BOOK 20)(PEN 6)(NOTEPAD 12)(TOTAL 38))
Thank you for your time
Here are 3 quite different solutions... one recursive, one iterative,
and one obscure. I won't do ALL your homework, so you will have to
figure out yourself how they work, which shouldn't be very hard.
Disclaimer: I'm quite new to Lisp myself, so there may be better and
more elegant solutions.
;;; 1
(defun total (lst)
(labels ((total-rec (sublst subtot)
(if sublst
(let* ((sub (car sublst))
(sum (* (cadr sub) (caddr sub))))
(cons `(,(car sub) ,sum)
(total-rec (cdr sublst) (+ subtot sum))))
`((total ,subtot)))))
(total-rec lst 0)))
;;; 2
(defun total (lst)
(let ((total 0)
(ret))
(dolist (elt lst (nreverse (push `(total ,total) ret)))
(let ((subtotal (* (cadr elt) (caddr elt))))
(push `(,(car elt) ,subtotal) ret)
(incf total subtotal)))))
;;; 3
(defun total (lst)
(append
(mapcar #'(lambda (e) (list (car e) (* (cadr e) (caddr e)))) lst)
`((total ,(apply #'+ (mapcar #'(lambda (elt) (* (cadr elt) (caddr
elt))) lst))))))
Gauche Scheme
(define (proc purchases)
(define grand-total 0)
(define (calc item quan price)
(let1 total (* quan price)
(inc! grand-total total)
(list item total)))
(append
(map: calc purchases)
(list (list 'total grand-total))))
(proc '((book 2 10) (pen 3 2) (notepad 1 12)))
===>
((book 20) (pen 6) (notepad 12) (total 38))
Given:
(define (map: func seq)
(map (lambda(x) (apply func x)) seq))
--
[T]he problem is that lispniks are as cultish as any other devout group and
basically fall down frothing at the mouth if they see [heterodoxy].
--- Kenny Tilton
The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham
| Date | Sujet | # | Auteur | |
| 8 Aug 25 |  Re: Lisp Function Problem | 1 | B. Pym |
Les messages affichés proviennent d'usenet.