Tag: Lisp

org-mode Observations 2014-02-24

org-mode style structural editing is available anywhere with the orgstruct-mode minor-mode running.
org-reveal exports Org documents to Reveal.js
org-protocol lets you use emacsclient as a sort of unlimited general purpose API vehicle.
When exporting to LaTeX, you may specify the table width as an attribute.
A Babel session may be “none” to prevent session creation.

color-theme-retro-green on Emacs 24

Wonder if anyone is using color-theme anymore; seems like wasted effort to just bail on all of the great themes in there. Today I wanted to get color-theme-retro-green at least working, and here is what it took against 6.5.5 of the Marmalade release:

(defun gcr/plist-to-alist (ls)
  "Convert a plist to an alist. Primarily for old color-theme themes."
  (let ((result nil))
    (while ls
      (add-to-list 'result (cons (car ls) (cadr ls)))
      (setq ls (cddr ls)))
    result))
(defalias 'plist-to-alist 'gcr/plist-to-alist)

Make a change in color-theme.el’s color-theme-retro-green to initialize face and faces with an empty list:

 ;; Build a list of faces without parameters
  (let ((old-faces (face-list))
        (faces '())
        (face '())
        (foreground (or color "green")))

Didn’t find a Github project to submit a patch so I emailed the owner.

One Emacs SML Workflow

Being partial to the full-REPL-reboot style of development (ala DrRacket) for most situations I wanted the same thing in Emacs with sml-mode. The value add is that you know all of your files are saved and that your environment is in a fresh and known state. I came up with this:

(defun gcr/sml-eval-buffer ()
  "Intelligently evaluate a SML buffer."
  (interactive)
  (gcr/save-all-file-buffers)
  (let ((sml-process (get-process "sml")))
    (when sml-process
      (quit-process sml-process)))
  (sleep-for 0.25)
  (let ((sml-buffer (get-buffer "*sml*")))
    (when sml-buffer
      (kill-buffer sml-buffer)))
  (sml-prog-proc-load-file buffer-file-name t))

Only to be delighted (though not surprised) to find yet another nearly identical approach here by wenjun.yan:

(defun isml ()
  "If sml repl exists, then restart it else create a new repl"
  (interactive)
  (when (get-buffer "*sml*")
    (with-current-buffer "*sml*"
      (when (process-live-p "sml")
        (comint-send-eof)))
    (sleep-for 0.2))
  (sml-run "sml" ""))

My urge to attain Emacs Comint mastery only grows.

Deleting trailing whitespace for auto savers

real-auto-save is a great package if you like that sort of thing. For example, I like every file to always be saved without me worrying about doing it myself, so I stick with the default save occurring every 10 seconds. A really nice function to call on write-file-hooks is delete-trailing-whitespace, but, with 10s saves this means that in the middle of typing you have spaces eaten and this is clearly unacceptable!
Here is an attempt at a tweaked cleanup function that cleans up every line in the file but for the current line on which your cursor sits:

(defun gcr/delete-trailing-whitespace ()
  "Apply delete-trailing-whitespace to everything but the current line."
  (interactive)
  (let ((first-part-start (point-min))
        (first-part-end (point-at-bol))
        (second-part-start (point-at-eol))
        (second-part-end (point-max)))
    (delete-trailing-whitespace first-part-start first-part-end)
    (delete-trailing-whitespace second-part-start second-part-end)))

Cask for the truly impatient

Thanks to some kind Emacsers I’m now in the modern age using Cask, and what ease it brings to using Emacs. It is truly a joy; anyone not using Emacs for fear of difficulty pulling in packages can let go of their hesitation. It is as easy as writing one config file, installing the packages, and adding a couple lines to your Emacs init script. Here are the basic steps:

  • Clone the cask repo.
  • Add the bin dir to your path.
  • Create a file named Cask, add it to your VCS, and create a link to it from your .emacs.d directory
  • Add a repo and packages to the file.
  • From your .emacs.d directory, run ‘cask’
  • Add the cask load and init to your init file.
  • Start Emacs.

Excellent work by that team.

Interactive Image Generation with Racket

Not sure whether I blogged about this or not already, but I sure could not find it so here goes.
A while back my buddy Bruce needed some randomly generated images in a particular format for a project. The specs were more of a “I’ll know it when I see it” kind of thing so I volunteered to help out and have some fun with Racket in the process.
The nifty part is that during development and also use you may preview the images directly inside of DrRacket. This feature made the work so, so fun (other editors do this, too).
Here is a copy of the code. Try running manual.scm and the image will show up in the REPL. If you run automatic.scm it will dump the image in /tmp.