How to rewrite code from Lisp to Scheme?

Question

It is impossible to rewrite the code from Lisp language to Scheme language, an error occurs, help to correct.
For example (cadr x) is equivalent to (car (cdr x)) a function (cadr x) is equivalent to (car (cdr x)), and I don't know how to interpret the numberp function.
Lisp code:

(defun deriv (f x)
  (cond ((numberp f) 0)
        ((eq f x) 1)
        ((eq (car f) '+) `(+ ,(deriv (cadr f) x) ,(deriv (caddr f) x)))
        ((eq (car f) '-) `(- ,(deriv (cadr f) x) ,(deriv (caddr f) x)))
        ((eq (car f) '*) `(+ (* ,(caddr f) ,(deriv (cadr f) x)) (* ,(cadr f) ,(deriv (caddr f) x))))
        ((eq (car f) '^) `(* (* ,(caddr f) (^ ,(cadr f) (- ,(caddr f) 1))) ,(deriv (cadr f) x)))))

How I tried to write this code on Scheme:

(define deriv (f x)
  (cond
        ((eq? f x) 1)
        ((eq? (car f) '+) '(+ ,(deriv (car (cdr f) x)) ,(deriv (car (cdr (cdr f) x)))))
        ((eq? (car f) '-) '(- ,(deriv (car (cdr f) x)) ,(deriv (car (cdr (cdr f) x)))))
        ((eq? (car f) '*) '(+ (* ,(car (cdr (cdr f))) ,(deriv (car (cdr f) x))) (* ,(car (cdr f)) ,(deriv (car (cdr (cdr f) x))))))
        ((eq? (car f) '^) '(* (* ,(car (cdr (cdr f))) (^ ,(car (cdr f)) (- ,(car (cdr (cdr f))) 1))) ,(deriv (car (cdr f)) x)))))

an error occurs

define: bad syntax (multiple expressions after identifier) in: (define deriv (f x) (cond ((eq? f x) 1) ((eq? (car f) (quote +)) (quote (+ (unquote (deriv (car (cdr f) x))) (unquote (deriv (car (cdr (cdr f) x))))))) ((eq? (car f) (quote -)) (quote (- (unquote (deriv (car (cdr f) x))) (unquote (deriv (car (cdr (cdr f) x))))))) ((eq? (car f) (quote *)) (quote (+ (* (unquote (car (cdr (cdr f)))) (unquote (deriv (car (cdr f) x)))) (* (unquote (car (cdr f))) (unquote (deriv (car (cdr (cdr f) x)))))))) ((eq? (car f) (quote ^)) (quote (* (* (unquote (car (cdr (cdr f)))) (^ (unquote (car (cdr f))) (- (unquote (car (cdr (cdr f)))) 1))) (unquote (deriv (car (cdr f)) x)))))))

p.s. Sorry for my English

Used, but I can't use them. These are the conditions of the job. Thanks :) — katesh
– katesh, Commented Apr 22, 2018 at 18:49
ah, OK, but it seems you do know how to deal with this: just use the chained applications of car and cdr according to the letters a and d: e.g., caddar -> (car (cdr (cdr (car . — Will Ness
– Will Ness, Commented Apr 22, 2018 at 18:59

Will Ness · Accepted Answer · 2018-04-22 18:29:37Z

1

You can use number? instead of numberp, and write

(define (func arg1 arg2 ...) ...)

in place of (defun func (arg arg2 ...) ...).

Also, don't be replacing the backquote ` with a simple quote '. Keep it.

answered Apr 22, 2018 at 18:29

Will Ness

71.6k10 gold badges105 silver badges192 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to rewrite code from Lisp to Scheme?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related