;COMMON-CHARACTER-SETS - Determine within reason the character sets supported by the implementation.
;Written in 2019 by Prince Trippy programmer@verisimilitudes.net .

;To the extent possible under law, the author(s) have dedicated all copyright
;and related and neighboring rights to this software to the public domain worldwide.
;This software is distributed without any warranty.

;You should have received a copy of the CC0 Public Domain Dedication along with this software.
;If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.

(in-package #:cl)

;Currently, I only have ASCII detection, but I'll be adding others soon.

(let ((set (make-array 128 :initial-contents (loop :for integer :from 0 :to 127
                                                   :collect (ignore-errors (code-char integer)))))
      (string (concatenate 'string ;I decided to keep the lines less than 100 columns.
                           " !\"#$%&'()*+,-./0123456789:;<=>?@"
                           "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                           "[\\]^_`"
                           "abcdefghijklmnopqrstuvwxyz"
                           "{|}~")))
  (and (>= char-code-limit 127)
       (notany 'null set)
       (loop :for integer :from #x30 :to #x39 :always (digit-char-p (aref set integer)))
       (loop :for integer :from 0 :to 31 :never (graphic-char-p (aref set integer)))
       (not (graphic-char-p (aref set 127)))
       (loop :for integer :from 32 :to 126
             :always (and (graphic-char-p (aref set integer))
                          (char= (aref set integer) (char string (- integer 32)))))
       (loop :for integer :from 65 :to 90
             :always (and (alpha-char-p (aref set integer))
                          (alpha-char-p (aref set (+ 32 integer)))
                          (char= (char-downcase (aref set integer)) (aref set (+ 32 integer)))))
       (pushnew :ascii *features*)))
.