;;; issn-verify.el --- verify ISSN -*- lexical-binding: t ;; ;;; Commentary: ;; ;; This Elisp package provides functions to verify ;; ISSN by computing their check digits. ;; ;; Author: Emanuel Berg (incal) ;; Created: 2020-09-06 ;; Keywords: bib, tex ;; License: GPL3+ ;; Package-Requires: ((cl-lib "1.0")) ;; URL: https://dataswamp.org/~incal/emacs-init/issn-verify.el ;; Version: 1.0.0 ;; ;; Also see: ;; ;; https://dataswamp.org/~incal/emacs-init/isbn-verify.el ;; ;; To install this package, with this file in ;; a buffer, do: ;; ;; M-x load-file RET RET ;; ;; International Standard Serial Number: ;; ;; ISO 3297, 1975 ;; ;; format: ;; ;; The Ring Magazine: ISSN 0035-5410 ;; d_1d_2d_3d_4-d_5d_6d_7c ;; d_i for i \in [1, 7] is an integer ;; c, the check digit, is 0..9 or X for 10 ;; ;; compute check digit c: ;; ;; c' = 8d_1*7d_2*6d_3*5d_4*4d_5*3d_6*2d_7 mod 11 ;; ;; { 0 c' = 0 ;; c = { ;; { 11 - c' else ;; ;;; Code: (require 'cl-lib) (defun issn--get-digits (issn) (let ((check-format (string-match-p "[[:digit:]]\\{4\\}-[[:digit:]]\\{3\\}[X[:digit:]]" issn) )) (if (and (= 9 (length issn)) check-format (zerop check-format) ) (let*((no-dash (replace-regexp-in-string "-" "" issn)) (issn-list (string-to-list no-dash)) (c-prop (car (last issn-list))) (c-prop-x (if (equal "X" c-prop) c-prop (- c-prop ?0))) (7-1st (butlast issn-list)) (nums (mapcar (lambda (c) (- c ?0)) 7-1st)) ) (append nums `(,c-prop-x)) ) (error "Malformed ISSN") ))) (defun issn-verify (issn) (interactive "sISSN: ") (let*((issn-lst (issn--get-digits issn)) (c-prop (car (last issn-lst))) (c-w (cl-loop with cwl = 0 for d in issn-lst for w downfrom 8 to 2 do (cl-incf cwl (* w d)) finally return cwl) ) (c-prime (mod c-w 11)) (c (if (zerop c-prime) 0 (- 11 c-prime) )) (c-x (if (= 10 c) "X" c)) ) (if (equal c-prop c-x) (message "(ISSN OK) %s" c-x) (error "Incorrect ISSN. Correct check digit is %s" c-prop) ))) ;; Bicycle Quarterly (issn-verify "1941-8809") ; (ISSN OK) 9 ;; Bicycling (issn-verify "1651-9744") ; (ISSN OK) 4 ;; Black Belt (issn-verify "0277-3066") ; (ISSN OK) 6 ;; Filter (issn-verify "1654-9813") ; (ISSN OK) 3 ;; Linux Pro (issn-verify "1471-5679") ; Incorrect ISSN. Correct check digit is 9 ;; National Geographic (issn-verify "2535-41241") ; Malformed ISSN ;; Outside (issn-verify "0278-433") ; Malformed ISSN ;; The Economist (issn-verify "0013-06a4") ; Malformed ISSN ;; The Ring (issn-verify "0035x5410") ; Malformed ISSN (provide 'issn-verify) ;;; issn-verify.el ends here