Coercing numbers to lists in common lisp

I'd like to turn integers into l开发者_如何学JAVAists. For example, 2245 => (2 2 4 5).

I dislike (coerce (write-to-string 2245) 'list) because it yields (#\2 #\2 #\4 #\5).

Help please?

(map 'list #'digit-char-p (prin1-to-string n))

works well.

(defun number-to-list (n)    
  (loop for c across (write-to-string n) collect (digit-char-p c)))

An alternative loop based solution.

Same as jon_darkstar but in common lisp. This fails for negative numbers, but trivial to amend.

(defun number-to-list (number)
  (assert (and (integerp number)
               (>= number 0)))
  (labels ((number-to-list/recursive (number) (print number)
             (cond
               ((zerop number)
                nil)
               (t
                (cons (mod number 10) 
                      (number-to-list/recursive (truncate (/ number 10))))))))
    (nreverse (number-to-list/recursive number))))

Common Lisp implementation for non-negative integers:

(defun number-to-list (n &optional tail)
  (if (zerop n)
    (or tail '(0))
    (multiple-value-bind (val rem)
                         (floor n 10)
      (number-to-list val (cons rem tail)))))

I don't really use common lisp, but I'd do it like this in Scheme. hopefully that can help?

(define (number-to-list x)
  (define (mod-cons x l)
     (if (zero? x)
         l
         (mod-cons (quotient x 10) (cons (remainder x 10) l))))
  (mod-cons x '()))

 (number-to-list 1234)

A variation on @Mark Cox's solution that also includes the '-' sign in case of negative integers. Inspired by @Terje Norderhaug's amendment to @rhombidodecahedron's solution, where negative numbers are represented by including a negative sign before the digits.

(defun number-to-numlist (number)
  "Converts an integer to a list of its digits. Negative numbers
are represented by a '-' sign prepended to the digits of its absolute value."
  (assert (integerp number))
  (labels ((collect-digits (number number-components list-of-numbers)
             (setf number-components (multiple-value-list (floor number 10)))
             (if (zerop number)
                 (or list-of-numbers '(0))
                 (collect-digits (first number-components) nil
                                 (cons (second number-components) list-of-numbers)))))
    (let ((number-list (collect-digits (abs number) nil nil)))
      (if (< number 0)
          (append '(-) number-list)
          number-list))))