Sha256: d2431731dc031f715d6bb1b76f7cf1c0dc657a61f5caea12a3459818638895f0
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Stored size: 943 Bytes
Contents
(defpackage #:trinary
(:use #:common-lisp)
(:export #:to-decimal))
(in-package #:trinary)
(defun to-decimal (string)
"Return the decimal value for STRING which is in trinary. If STRING
is not a valid trinary number then return 0."
(or (ignore-errors (parse-integer string :radix 3))
0))
;;;
;;; Another possible implementation, if one wanted to reimplement
;;; PARSE-INTEGER
;;;
;; (defun to-decimal (string)
;; (loop with revstr = (reverse string)
;; for idx below (length string) and c across revstr
;; for digit = (digit-char-p c 3)
;; if (not digit) return 0
;; else summing (* digit (expt 3 idx))))
;;;
;;; Another possible implementation but has a security flaw.
;;; Ponder what would happen if STRING was
;;; "#.(delete-file \"/etc/passwd\")"
;;;
;; (defun to-decimal (string)
;; (let* ((*read-base* 3)
;; (value (read-from-string string)))
;; (if (typep value 'number) value 0)))
Version data entries
396 entries across 396 versions & 1 rubygems