I have used Emacs since 1986 or so, daily since 1989 (with smaller breaks while working at companies where it was not available). I had no idea this exists.

Here is my first CCL program.

   (define-ccl-program hw
     '(1
       (loop
        (write r0 [72 101 108 111])
        (r1 += 1)
        (if (r1 == 3) (repeat) ())
        (r0 += 1)
        (if (r0 < 4) (repeat) (break))
        )
       )
       )

   (ccl-execute-on-string
   'hw
   [0 0 0 0 0 0 0 0 1] "")

Judging by the name and by these opcodes

https://github.com/emacs-mirror/emacs/blob/7cb77385d38b96377...

it seems to be intended for character set conversion especially JIS.

• usr1106

  yesterday at 11:23 PM

  More documentation in https://github.com/emacs-mirror/emacs/blob/7cb77385d38b96377...

  The directory is lisp/international, that already tells something

     ;; CCL is used for code conversion at process I/O and file I/O for
     ;; non-standard coding-systems.  In addition, it is used for
     ;; calculating code points of X fonts from character codes.
  

  And

     $ find /usr/share/emacs/26.3/lisp/ \! -name ccl.el.gz -name \*.el.gz -exec zgrep ccl- {} +
     /usr/share/emacs/26.3/lisp/obsolete/pgg-parse.el.gz:(when (fboundp 'define-ccl-program)
     /usr/share/emacs/26.3/lisp/obsolete/pgg-parse.el.gz:  (define-ccl-program pgg-parse-crc24
     /usr/share/emacs/26.3/lisp/obsolete/pgg-parse.el.gz:      (ccl-execute-on-string pgg-parse-crc24 h string)
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:specified by the attributes `:ccl-decoder' and `:ccl-encoder'.
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:`:ccl-decoder' (required if :coding-type is `ccl')
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:VALUE is a CCL program name defined by `define-ccl-program'.  The
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:`:ccl-encoder' (required if :coding-type is `ccl')
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:VALUE is a CCL program name defined by `define-ccl-program'.  The
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:        '(:ccl-decoder
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:          :ccl-encoder
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:    (plist-put properties :ccl-decoder (car flags))
     /usr/share/emacs/26.3/lisp/international/mule.el.gz:    (plist-put properties :ccl-encoder (cdr flags))))
     /usr/share/emacs/26.3/lisp/language/vietnamese.el.gz:;;  '(ccl-decode-vps . ccl-encode-vps)
     /usr/share/emacs/26.3/lisp/language/ethiopic.el.gz:(define-ccl-program ccl-encode-ethio-font
     /usr/share/emacs/26.3/lisp/language/ethiopic.el.gz:(setq font-ccl-encoder-alist
     /usr/share/emacs/26.3/lisp/language/ethiopic.el.gz:      (cons (cons (purecopy "ethiopic") ccl-encode-ethio-font) font-ccl-encoder-alist))
  

  Mule was non-ASCII support in the 1990s before Unicode was a thing.

The source code mentioned in the article is well documented and an interesting read too; e.g.:

https://github.com/emacs-mirror/emacs/blob/master/src/ccl.c

Interesting. I've been using Emacs for 6 years and have never heard of CCL. I would love to read a book on all the strange and fascinating code that Emacs has accumulated over the years.

• sourcepluck

  yesterday at 8:12 PM

  Yes, it seems ripe for quasi-archaelogical investigations. One tidbit that I couldn't believe was that Julian Assange had written an early version of Windmove, or an addition to an early version, or something along those lines.

  I've nosed through some of the elisp files for the games - little goldmines everywhere in there.

  • thih9

    yesterday at 9:05 PM

    Looks like the details are in the file itself:

    > Special thanks to Julian Assange (proff@iq.org), whose change-windows-intuitively.el predates Windmove, and provided the inspiration for it.

    Source: https://github.com/emacs-mirror/emacs/blob/4823fa1077e4330bd...

    change-windows-intuitively: http://quimby.gnus.org/s/change-windows-intuitively.el

    • sourcepluck

      today at 12:13 AM

      Ah thank you, yes, that's it. A precursor to windmove, then. Very nice!

  • Conscat

    yesterday at 9:54 PM

    I recently played Emacs tetris, and I was confused by how the tetrominos were selected so I dove into the source code to impress my boyfriend. It turns out that the tetrominos' behavior is configurable with a defcustom, but by default it chooses to play without the bag rule, making their tetris hard to take seriously as an implementation for competitive play >:c

    • sourcepluck

      today at 12:18 AM

      A. And was he impressed? My S.O. tends to have mixed reactions if I go on about source code too much. It's a fine line. She's an excellent tetris player though, so maybe this would get a pass.

      B. I am not a big tetris player (too afraid of the inevitable addiction), but had a game there to see, and am now looking at the source code. ~tetris-allow-repetitions~ just has to be changed to nil, and then it does the correct bag rule behaviour?

      C. I wonder why Emacs' tetris default is without the bag rule then... maybe you could submit a patch and propose a tournament? I only learned recently that the platform used for official tournaments is the NES version of Tetris, and now I'm learning that they use the bag rule. Tetris is more serious than I ever knew.

  • usr1106

    today at 12:04 AM

    Not only archaeological. Some new Android stuff was implemented in CCL only last year.

Title should say (2019)