;;; -*- Mode:LISP; Base:10; Readtable:CL -*-

;;; Given the list of 1-800 phone exchanges, crank out the combinations of numbers

(defvar fourdigits "LISP")

(defvar nls
	'((1 1 1 1)
	  (2 a b c)
	  (3 d e f)
	  (4 g h i)
	  (5 j k l)
	  (6 m n o)
	  (7 p r s)
	  (8 t u v)
	  (9 w x y)))

(defconst ex
	  '(223 227 248 255
		262 322 323
		327 332 338
		342 346 356
		422 426 445
		451 458 521
		522 528 527
		533 537 541
		542 543 544
		548 553 622
		624 634 635
		637 638 642
		648 722 752
		782 822 832
		852 872 922
		942 962 992))

(defun charnum(c)
  (- c #\0))

(defun chardigits(c)
  (cdr(assoc c nls :test #'(lambda(a b)(equal (charnum a) b)))))

(defun combs1(n)
  (let((x (format nil "~d" n)))
    (let((x1 (aref x 0))
	 (x2 (aref x 1))
	 (x3 (aref x 2)))
      (format t "~&N=~s" n)
      (dolist (a (chardigits x1))
	(dolist (b (chardigits x2))
	  (dolist (c (chardigits x3))
	    (format t "~&  1-800-~a~a~a-~a" a b c fourdigits)))))))

(defun combs(&optional (l ex))
  (mapcar #'combs1 l))