Factorions: Difference between revisions

=={{header|Common Lisp}}==

<lang lisp>(defparameter *bases* '(9 10 11 12))

(defparameter *limit* 1500000)

(defun ! (n) (apply #'* (loop for i from 2 to n collect i)))

(defparameter *digit-factorials* (mapcar #'! (loop for i from 0 to (1- (apply #'max *bases*)) collect i)))

(defun fact (n) (nth n *digit-factorials*))

(defun digit-value (digit)

(let ((decimal (digit-char-p digit)))

(cond ((not (null decimal)) decimal)

((char>= #\Z digit #\A) (+ (char-code digit) (- (char-code #\A)) 10))

((char>= #\z digit #\a) (+ (char-code digit) (- (char-code #\a)) 10))

(t nil))))

(defun factorionp (n &optional (base 10))

(= n (apply #'+

(mapcar #'fact

(map 'list #'digit-value

(write-to-string n :base base))))))

(loop for base in *bases* do

(let ((factorions

(loop for i from 1 while (< i *limit*) if (factorionp i base) collect i)))

(format t "In base ~a there are ~a factorions:~%" base (list-length factorions))

(loop for n in factorions do

(format t "~c~a" #\Tab (write-to-string n :base base))

(if (/= base 10) (format t " (decimal ~a)" n))

(format t "~%"))

(format t "~%")))</lang>

{{Out}}

<pre>In base 9 there are 3 factorions:

1 (decimal 1)

2 (decimal 2)

62558 (decimal 41282)

In base 10 there are 4 factorions:

1

2

145

40585

In base 11 there are 5 factorions:

1 (decimal 1)

2 (decimal 2)

24 (decimal 26)

44 (decimal 48)

28453 (decimal 40472)

In base 12 there are 2 factorions:

1 (decimal 1)

2 (decimal 2)

</pre>