Common Lisp Function

Question

I want create a function that verify if the numbers of a list fall between the range of 1 and 10 (including the 1 and 10). If they do, I wanted to add it to a new list that I created. However, if they fail to fall within the range I decided to convert them so they fit in rather than discarding them (by adding (1+ (random 10)).

(defun fit (lst)

  "(lst) check every number if it fits the range (1-10)"

  (do ((fit lst (cdr fit))

       (range nil))
      ((null fit) (reverse range))
    (if (and (>= fit 1) (=< fit 10))
        (seft ((cons fit range))))
       (or (< fit 1) (> fit 10)) 
           (cons (+ fit (1+ (random 10))) range)))

The codes start from (defun fit...). However, it's not working and I'm at short of any type of changes I can do mainly because of my limited knowledge. Any help or insight will be greatly appreciated. Thank you.

drysdam · Accepted Answer · 2011-11-04 20:16:18Z

2

I think you are trying to do too much work yourself. Think higher functions. Your problem statement already tells you half of it: "check every number if it fits in the range 1-10".

How about using (every)? Then you need to pass it a function that checks a single number. Probably lambda...

answered Nov 4, 2011 at 20:16

drysdam

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Comments

lindelof · Accepted Answer · 2011-11-04 20:39:58Z

1

How about this:

(defun fit (list)
  (cond ((null list) '())
        ((< (car list) 1)
         (fit (cons (+ (car list) (random 10)) (cdr list))))
        ((> (car list) 10)
         (fit (cons (- (car list) (random 10)) (cdr list))))
        (t (cons (car list) (fit (cdr list))))))

answered Nov 4, 2011 at 20:39

lindelof

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2 Comments

user1030365 Over a year ago

THANK YOU!!! You've given back my sanity... I didn't think of using cond. I figured if i'm gonna be looping through it the better option is DO. I appreciate your time and effort so much.

Vatine Over a year ago

Using LOOP and COLLECT (or IF and COLLECT) is an optin as well.

Svante · Accepted Answer · 2011-11-09 15:18:07Z

I think that you want to apply a make-fitting function on each element.

(defun make-fitting (n)
  (loop (incf n
              (cond ((> n 10) (- (1+ (random 10))))
                    ((< n 1) (1+ (random 10)))
                    (t (return-from make-fitting n))))))

(defun fit (list)
  (mapcar #'make-fitting list))

If you anticipate different limits, you should give them as possibly optional parameters:

(defun make-fitting (n &optional (low 1) (high 10))
  (let ((step-size (1+ (- high low))))
    (flet ((random-step (size)
             (1+ (random size))))
      (loop (incf n
                  (cond ((> n high) (- (random-step step-size)))
                        ((< n low) (random-step step-size))
                        (t (return-from make-fitting n))))))))

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