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2023-03-06 Emacs news

| emacs, emacs-news

[2023-03-06 Mon] Update: Added https://www.fredgruber.org/post/ess_emacs_default_r_session/ to Org Mode section.

Links from reddit.com/r/emacs, r/orgmode, r/spacemacs, r/planetemacs, Hacker News, lobste.rs, planet.emacslife.com, YouTube, the Emacs NEWS file, Emacs Calendar, emacs-devel, and lemmy/c/emacs. Thanks to Andrés Ramírez for emacs-devel links. Do you have an Emacs-related link or announcement? Please e-mail me at sacha@sachachua.com. Thank you!

View or add comments (Disqus), or e-mail me at sacha@sachachua.com

2023-02-27 Emacs news

| emacs, emacs-news

Links from reddit.com/r/emacs, r/orgmode, r/spacemacs, r/planetemacs, Hacker News, lobste.rs, planet.emacslife.com, YouTube, the Emacs NEWS file, Emacs Calendar, emacs-devel, and lemmy/c/emacs. Thanks to Andrés Ramírez for emacs-devel links. Do you have an Emacs-related link or announcement? Please e-mail me at sacha@sachachua.com. Thank you!

View or add comments (Disqus), or e-mail me at sacha@sachachua.com

2023-02-20 Emacs news

| emacs, emacs-news

Links from reddit.com/r/emacs, r/orgmode, r/spacemacs, r/planetemacs, Hacker News, lobste.rs, planet.emacslife.com, YouTube, the Emacs NEWS file, Emacs Calendar, emacs-devel, and lemmy/c/emacs. Thanks to Andrés Ramírez for emacs-devel links. Do you have an Emacs-related link or announcement? Please e-mail me at sacha@sachachua.com. Thank you!

View or add comments (Disqus), or e-mail me at sacha@sachachua.com

2023-02-13 Emacs news

| emacs, emacs-news

Links from reddit.com/r/emacs, r/orgmode, r/spacemacs, r/planetemacs, Hacker News, lobste.rs, planet.emacslife.com, YouTube, the Emacs NEWS file, Emacs Calendar, emacs-devel, and lemmy/c/emacs. Thanks to Andrés Ramírez for emacs-devel links. Do you have an Emacs-related link or announcement? Please e-mail me at sacha@sachachua.com. Thank you!

View or add comments (Disqus), or e-mail me at sacha@sachachua.com

Using rubik.el to make SVG last-layer diagrams from algorithms

| cubing, emacs, org

So I checked out emacs-cube, but I had a hard time figuring out how to work with the data model without getting into all the rendering because it figures "left" and "right" based on camera position. rubik.el seemed like an easier starting point. As far as I can tell, the rubik-cube-state local variable is an array with the faces specified as 6 groups of 9 integers in this order: top, front, right, back, left, bottom, with cells specified from left to right, top to bottom.

First, I wanted to recolour rubik so that it matched the setup of the Roofpig JS library I'm using for animations. 

(defconst my-cubing-rubik-faces "YRGOBW")
;; make it match roofpig's default setup with yellow on top and red in front
(defconst rubik-faces [rubik-yellow
                       rubik-red
                       rubik-green
                       rubik-orange
                       rubik-blue
                       rubik-white])

Here are some functions to apply an algorithm (or actually, the inverse of the algorithm, which is useful for exploring a PLL case): 

(defun my-cubing-normalize (alg)
  "Remove parentheses and clean up spaces in ALG."
  (string-trim
   (replace-regexp-in-string "[() ]+" " " alg)))

(defun my-cubing-reverse-alg (alg)
  "Reverse the given ALG."
  (mapconcat
   (lambda (step)
     (if (string-match "\\`\\([rludfsbRLUDFSBxyz]\\)\\(['i]\\)?\\'" step)
         (concat (match-string 1 step)
                 (if (match-string 2 step)
                     ""
                   "'"))
       step))
   (reverse
    (split-string (my-cubing-normalize alg) " "))
   " "))

(defun my-cubing-rubik-alg (alg)
  "Apply the reversed ALG to a solved cube.
Return the rubik.el cube state."
  (let ((reversed (my-cubing-reverse-alg alg)))
    (seq-reduce
     (lambda (cube o)
       (when (intern (format "rubik-%s"
                             (replace-regexp-in-string "'" "i" o)))
         (unless (string= o "")
           (rubik-apply-transformation
            cube
            (symbol-value
             (intern
              (format "rubik-%s"
                      (replace-regexp-in-string "'" "i" o)))))))
       cube)
     (split-string reversed " ")
     (rubik-make-initial-cube))))

Then I got the strings specifying the side colours and the top colours in the format that I needed for the SVG diagrams. I'm optimistically using number-sequence here instead of hard-coding the numbers so that I can figure out how to extend the idea for 4x4 someday. 

(defun my-cubing-rubik-top-face-strings (&optional cube)
  ;; edges starting from back left
  (let ((cube (or cube rubik-cube-state)))
    (list
     (mapconcat
      (lambda (i)
        (char-to-string (elt my-cubing-rubik-faces (aref cube i))))
      (append
       (reverse (number-sequence (* 3 9) (+ 2 (* 3 9))))
       (reverse (number-sequence (* 2 9) (+ 2 (* 2 9))))
       (reverse (number-sequence (* 1 9) (+ 2 (* 1 9))))
       (reverse (number-sequence (* 4 9) (+ 2 (* 4 9))))))
     (mapconcat
      (lambda (i)
        (char-to-string (elt my-cubing-rubik-faces (aref cube i))))
      (number-sequence 0 8)))))

Then theoretically, it can make a diagram like this: 

(defun my-cubing-rubik-last-layer-with-sides-from-alg (alg &optional arrows)
  (apply 'my-cubing-last-layer-with-sides
         (append
          (my-cubing-rubik-top-face-strings (my-cubing-rubik-alg alg))
          (list
           arrows))))

So I can invoke it with: 

(my-cubing-rubik-last-layer-with-sides-from-alg
 "R U R' F' R U R' U' R' F R2 U' R' U'"
 '((1 7 t) (2 8 t)))
last-layer.svg

It's also nice to be able to interactively step through the algorithm. I prefer a more compact view of the undo/redo state. 

;; Override undo information
(defun rubik-display-undo ()
  "Insert undo information at point."
  (cl-loop with line-str = "\nUndo: "
           for cmd in (reverse (cdr rubik-cube-undo))
           for i = 1 then (1+ i)
           do (progn
                (setq line-str (concat line-str (format "%s " (get cmd 'name))))
                (when (> (length line-str) fill-column)
                  (insert line-str)
                  (setq line-str (concat "\n" (make-string 6 ?\s)))))
           finally (insert line-str)))

;; Override redo information
(defun rubik-display-redo ()
  "Insert redo information at point."
  (cl-loop with line-str = "\nRedo: "
           for cmd in (cdr rubik-cube-redo)
           for i = 1 then (1+ i)
           do (progn
                (setq line-str (concat line-str (format "%s " (get cmd 'name))))
                (when (> (length line-str) fill-column)
                  (insert line-str)
                  (setq line-str (concat "\n" (make-string 6 ?\s)))))
           finally (insert line-str)))
  
(defun my-cubing-convert-alg-to-rubik-commands (alg)
  (mapcar
   (lambda (step)
     (intern
      (format "rubik-%s-command"
              (replace-regexp-in-string "'" "i" step))))
   (split-string (my-cubing-normalize alg) " ")))

(rubik-define-commands
  rubik-U "U" rubik-U2 "U2" rubik-Ui "U'"
  rubik-F "F" rubik-F2 "F2" rubik-Fi "F'"
  rubik-R "R" rubik-R2 "R2" rubik-Ri "R'"
  rubik-L "L" rubik-L2 "L" rubik-Li "L'"
  rubik-B "B" rubik-B2 "B" rubik-Bi "B'"
  rubik-D "D" rubik-D2 "D" rubik-Di "D'"
  rubik-x "x" rubik-x2 "x" rubik-xi "x'"
  rubik-y "y" rubik-y2 "y" rubik-yi "y'"
  rubik-z "z" rubik-z2 "z2" rubik-zi "z'")

(defun my-cubing-rubik-set-to-alg (alg)
  (interactive "MAlg: ")
  (rubik)
  (fit-window-to-buffer)
  (setq rubik-cube-state (my-cubing-rubik-alg alg))
  (setq rubik-cube-redo (append (list 'redo)
                                (my-cubing-convert-alg-to-rubik-commands
                                 alg)))
  (setq rubik-cube-undo '(undo))
  (rubik-draw-all)
  (display-buffer (current-buffer)))

And now I can combine all those pieces together in a custom Org link type that will allow me to interactively step through an algorithm if I open it within Emacs and that will export to a diagram and an animation. 

(org-link-set-parameters
 "3x3"
 :follow #'my-cubing-rubik-open
 :export #'my-cubing-rubik-export)

(defun my-cubing-rubik-open (path &optional _)
  (my-cubing-rubik-set-to-alg (if (string-match "^\\(.*\\)\\?\\(.*\\)$" path)
                                  (match-string 1 path)
                                path))) 
  
(defun my-cubing-rubik-export (path _ format _)
  "Export PATH to FORMAT."
  (let (alg arrows params)
    (setq alg path)
    (when (string-match "^\\(.*\\)\\?\\(.*\\)$" path)
      (setq alg (match-string 1 path)
            params (org-protocol-convert-query-to-plist (match-string 2 path))
            arrows
            (mapcar (lambda (entry)
                      (mapcar 'string-to-number
                               (split-string entry "-"))) 
                    (split-string
                     (plist-get params :arrows) ","))))
    (concat
     (my-cubing-rubik-last-layer-with-sides-from-alg
      alg
      arrows)
     (format "<div class=\"roofpig\" data-config=\"base=PLL|alg=%s\"></div>"
             (my-cubing-normalize alg)))))

Let's try that with this F-perm, which I haven't memorized yet: 

[[3x3:(R' U' F')(R U R' U')(R' F R2 U')(R' U' R U)(R' U R)?arrows=1-7,7-1,2-8,8-2]]

At some point, I'd like to change the display for rubik.el so that it uses SVGs. (Or the OpenGL hacks in https://github.com/Jimx-/emacs-gl, but that might be beyond my current ability.) In the meantime, this might be fun.

In rubik.el, M-r redoes a move and M-u undoes it. Here's what it looks like with my tweaked interface:

output-2023-02-09-15:25:42.gif
Figure 1: Animated GIF of rubik.el stepping through an F-perm
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2023-02-06 Emacs news

| emacs, emacs-news

Links from reddit.com/r/emacs, r/orgmode, r/spacemacs, r/planetemacs, Hacker News, lobste.rs, planet.emacslife.com, YouTube, the Emacs NEWS file, Emacs Calendar, emacs-devel, and lemmy/c/emacs. Thanks to Andrés Ramírez for emacs-devel links. Do you have an Emacs-related link or announcement? Please e-mail me at sacha@sachachua.com. Thank you!

View or add comments (Disqus), or e-mail me at sacha@sachachua.com

Using Org Babel to learn Rubik's cube algorithms

| emacs, cubing, org

A+ has started learning Rubik's cube algorithms for permutation of the last layer (PLL) algorithms for the Rubik's cube. To help her focus on just a few at a time instead of getting distracted by the long list in the Cubeskills PLL PDF, I made a page that listed the algorithms that she was working on so that I could export it with ox-hugo to the mini-site I made for her interests.

She sometimes gets a little confused about clockwise and counter-clockwise, so I used Roofpig to add an animated view of the algorithm that she can step through. I wanted to make it easier for her to follow the algorithm without constantly moving her hands from the cube to the tablet or looking up and down all the time, but I didn't want to recompile the source just yet. I used the roofpig_and_three.min.js file and hacked speech synthesis into it by modifying the object prototype. For example, here's the Org source for adding a Jb perm: 

#+begin_export html
<div class="roofpig" data-config="base=PLL|alg=R U R' F' R U R' U' R' F R2 U' R' U'"></div>
#+end_export

and here's what it looks like. Might only look nice on my website, and I added speech synthesis so you may want to mute it if you need to be quiet.

Code for setting up Roofpig with speech synthesis
<!--  -*- mode: web -*- -->
<style>
 .roofpig { max-width: 400px; margin-bottom: 80px; }
 </style>
 <script>

  function waitToAddSpeech() {
    if (window.cubesSpeakMoves || !window.speechSynthesis) return;
    if (window.CubeAnimation) {
      window.cubesSpeakMoves = true;
        addSpeechToCubeAnimations();
      } else {
        setTimeout(setUpCubes, 300);
      }
  }
  
  function setUpCubes() {
    if (!document.querySelector('script.roofpig')) {
      var script = document.createElement('script');
      script.setAttribute('src', '/blog/2023/02/using-org-babel-to-learn-rubik-s-cube-algorithms/roofpig_and_three.min.js');
      script.classList.add('roofpig');
      document.head.appendChild(script);
      waitToAddSpeech();
    }
  }
  
  function addSpeechToCubeAnimations() {
   if (!window.CubeAnimation || !window.CubeAnimation['by_id'] || !window.CubeAnimation['by_id'][1]) return;
   var cachedFunc = Object.getPrototypeOf(CubeAnimation['by_id'][1].dom).alg_changed;
   Object.getPrototypeOf(CubeAnimation['by_id'][1].dom).alg_changed = function() {
     if (arguments[4].past.length > lastNoted.length) {
       let moves = arguments[4].past.split(' ');
       let lastMove = moves[moves.length - 1];
       // is it lower-case? speak lowercase explicitly
       if (lastMove.match(/[rludbf]/)) {
         lastMove = 'lower ' + lastMove;
       } else { // avoid awkward-sounding moves like "capital R"
         lastMove = lastMove.toLowerCase();
       }
       lastMove = lastMove.replace(/'/, ' prime');
      window.speechSynthesis.speak(new SpeechSynthesisUtterance(lastMove));
     } else {
       console.log('going backwards');
     }
     lastNoted = arguments[4].past;
     return cachedFunc.apply(this, arguments);
   }
 }
 ROOFPIG_CONF_F2L = "solved=U*|hover=none|colored=U-|flags=canvas,showalg|speed=1000";
 ROOFPIG_CONF_PLL = "solved=U-|hover=near|colored=U*|flags=canvas,showalg|speed=1000";
 var lastNoted = '';
window.addEventListener('load', setUpCubes);
</script>

I also wanted to include diagrams to make it easier for her to choose the right algorithm and position the cube the right way at the beginning, but I didn't want to fuss around with lots of screenshots and little files. It turns out you can define arrows in SVG pretty easily, so I wrote some Emacs Lisp functions to generate those types of diagrams. First I started with just the arrows. 

(my-cubing-last-layer-arrows '((2 8 t) (5 7 t)))
arrows.svg

For practising recognition, I wanted to also include the colors on top and on the sides: 

(my-cubing-last-layer-with-sides "OOGRROGGRBBB" "YYYYYYYYY" '((2 8 t) (5 7 t)))
colors.svg

Emacs Lisp functions for cubing diagrams
;; Start of cubing code
(defun my-cubing-pos (size n i)
  (list
   (* (/ size n) (% i n))
   (* (/ size n) (/ i n))))
  
(defun my-cubing-last-layer-arrows (arrows)
  "Draw ARROWS.
Arrows are defined as a list of lists of the form
((from to) (from to t) ...). Ex: '(my-cubing-last-layer-arrows '((3 1 t) (2 8 t)))
Cells are numbered from left to right, top to bottom, with the top left box being 0.
"
  (let* ((size 99)
         (n 3)
         (arrow-color "#000")
         (svg (svg-create size size)))
    (svg--append
     svg
     (dom-node
      'defs
      nil
      (dom-node
       'marker
       '((id . "arrowhead")
         (markerWidth . "10")
         (markerHeight . "7")
         (refX . "0")
         (refY . "3.5")
         (orient . "auto-start-reverse"))
       (dom-node
        'polygon
        `((fill . ,arrow-color)
          (points . "0 0, 4 3.5, 0 7")))
       )))
    (dotimes (i (* n n))
      (let ((pos (my-cubing-pos size n i)))
        (svg-rectangle
         svg
         (car pos)
         (cadr pos)
         (/ size n)
         (/ size n)
         :fill "#fff"
         :stroke-width 1
         :stroke "#666")))
    (dolist (arrow arrows)
      (let ((from (car arrow))
            (to (cadr arrow)))
        (apply 'svg-line
               (append
                (list svg)
                (mapcar (lambda (o) (+ o (/ size (* 2 n))))
                        (my-cubing-pos size n from))
                (mapcar (lambda (o) (+ o (/ size (* 2 n))))
                        (my-cubing-pos size n to))
                (list
                 :stroke-width 2
                 :stroke arrow-color
                 :marker-start (if (elt arrow 2) "url(#arrowhead)")
                 :marker-end "url(#arrowhead)")))))
    (with-temp-buffer
      (svg-print svg)
      (buffer-string))))

(defvar my-cubing-colors '((?R  . "#ff0000")
                           (?G  . "#00ff00")
                           (?B  . "#0000ff")
                           (?O  . "#ed7117")
                           (?Y  . "#ffff00")
                           (?W  . "#ffffff")
                           (?\? . "#666666")))

(defun my-cubing-last-layer-with-sides (sides top arrows)
  "Draw a diagram of the top of the cube.
The style is similar to https://www.cubeskills.com/uploads/pdf/tutorials/pll-algorithms.pdf .
SIDES is a string specifying colors going clockwise from the back-left side.
TOP is a string specifying colors going from left to right, top to bottom.
Arrows are defined as a list of lists of the form ((from to) (from to t) ...).
Cells are numbered from left to right, top to bottom, with the top left box being 0.
Ex: (my-cubing-last-layer-with-sides \"ORRBOOGGGRBB\" \"YYYYYYYYY\" '((3 1 t) (2 8 t)))
"
  (let* ((size 99)
         (n 3)
         (side-size 10)
         (cell-size (/ (- size (* 2 side-size)) n))
         (arrow-color "#000")
         (svg (svg-create size size)))
    (svg--append
     svg
     (dom-node
      'defs
      nil
      (dom-node
       'marker
       '((id . "arrowhead")
         (markerWidth . "10")
         (markerHeight . "7")
         (refX . "0")
         (refY . "3.5")
         (orient . "auto-start-reverse"))
       (dom-node
        'polygon
        `((fill . ,arrow-color)
          (points . "0 0, 4 3.5, 0 7"))))))
    ;; Draw the sides. It's a string of colors going clockwise from back left
    (when sides
      (dotimes (i (* n 4))
        (apply 'svg-rectangle
               (append
                (list svg)
                (pcase (/ i n)
                  (0 (list (+ (* (% i n) cell-size) side-size)
                           0
                           cell-size
                           side-size))
                  (1 (list (+ side-size (* n cell-size))
                           (+ (* (% i n) cell-size) side-size)
                           side-size
                           cell-size))
                  (2 (list (+ (* (- n (% i n) 1) cell-size) side-size)
                           (+ (* n cell-size) side-size)
                           cell-size
                           side-size))
                  (3 (list 0
                           (+ (* (- n (% i n) 1) cell-size) side-size)
                           side-size
                           cell-size)))
                (list
                 :stroke-width 1
                 :stroke "#666"
                 :fill (assoc-default (elt sides i)
                                      my-cubing-colors
                                      'eq
                                      (assoc-default ?\? my-cubing-colors)))))))
    ;; Draw the top face specified by a string of colors going from left to right, top to bottom
    (dotimes (i (* n n))
      (let ((pos (my-cubing-pos (* cell-size n) n i)))
        (svg-rectangle
         svg
         (+ side-size (car pos))
         (+ side-size (cadr pos))
         cell-size
         cell-size
         :fill (if top
                   (assoc-default (elt top i) my-cubing-colors
                                  'eq
                                  (assoc-default ?\? my-cubing-colors))
                 (assoc-default ?\? my-cubing-colors))
         :stroke-width 1
         :stroke "#666")))
    ;; Draw the arrows
    (dolist (arrow arrows)
      (let ((from (car arrow))
            (to (cadr arrow)))                  
        (apply 'svg-line
               (append
                (list svg)
                (mapcar (lambda (o) (+ side-size o (/ cell-size 2)))
                        (my-cubing-pos (* n cell-size) n from))
                (mapcar (lambda (o) (+ side-size o (/ cell-size 2)))
                        (my-cubing-pos (* n cell-size) n to))
                (list
                 :stroke-width 2
                 :stroke arrow-color
                 :opacity 0.5
                 :marker-start (if (elt arrow 2) "url(#arrowhead)")
                 :marker-end "url(#arrowhead)")))))
    (with-temp-buffer
      (svg-print svg)
      (buffer-string))))
;; end of cubing code

I'll probably need to tweak the arrows when we eventually get to the G perms, but we're still a long way off. And it would probably be pretty cool to be able to generate the colours by going backwards from the algorithm, maybe building on top of emacs-cube, so that I can write my own notes about recognizing the in-between steps and recovering from the typical mistakes we make. (That wasn't around the last time I wrote about Emacs and cubing. Thanks to Akib for making and sharing it!) I'm curious about this LaTeX approach, too, but that can wait for another day.

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