same sound random sort everywhere (was: Re: avoid narrow-to-region (was: Re: replace-regexp))

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

Here we see it implemented for strings. If the nshuff
algorithm is sound data type should - you guessed it - not
influence anything in either way to make it more or less
sound. See comments.

;;; -*- lexical-binding: t -*-
;;;
;;; this file:
;;;   http://user.it.uu.se/~embe8573/emacs-init/random-generic.el
;;;   https://dataswamp.org/~incal/emacs-init/random-generic.el

(require 'cl-lib)

;; add more datatypes here... (for each type, one disassembler,
;; one call to nshuff, and one assembler is needed)

(defun string-random (s)
  (let*((str-lst (string-to-list s))
        (lst     (nshuff str-lst))
        (str-shuff (mapconcat (lambda (c) (char-to-string c)) lst "")) )
    str-shuff) )
;; (string-random "Elisp is my favorite E")

;; ... all use the same random-sort algorithm

(defun nshuff (sq)
  (cl-loop for i from (length sq) downto 2
           do (cl-rotatef
               (elt sq (cl-random i))
               (elt sq (1- i)) ))
  sq)
;; (nshuff '(a b c)) ; (b c a) (a b c) (b c a) ...

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