93 lines
4 KiB
Markdown
93 lines
4 KiB
Markdown
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---
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title: Emacs and extensibility
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date: 2015-10-06
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---
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Update: I've put the small Emacs tools I have written to a
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[gist](https://gist.github.com/91c38ddde617b98ffbcb).
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I have been using Emacs for some time, and I really love it. The
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amount of power it has, and the customizability is incredible. What
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other editor allow you to connect to a server over SSH and edit files,
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which is what I am doing to write this post. How many editors or IDE's
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have support for so many languages?
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<!--more-->
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One thing I didn't know in the past, however, is extensibility of
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Emacs. I mean, I do use a lot of packages, but I had never written
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Elisp and I didn't know how hard or easy it would be. But after
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starting to learn Clojure a bit, and feeling more comfortable with
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lots of parenthesis, I decided to extend Emacs a bit to make it fit
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myself better.
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The first thing I added is an "insert date" function. I use Emacs to
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take notes during lessons -using Org-mode- and I start every note with
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the date of the lesson. Sure, glancing at the date to the corner of my
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screen and writing it down takes just a few seconds, but why not write
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a command to do it for me? Here is what I came up with:
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```commonlisp
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(defun insert-current-date ()
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"Insert the current date in YYYY-MM-DD format."
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(interactive)
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(shell-command "date +'%Y-%m-%d'" t))
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```
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Now that was easy and convenient. And being able to write my first
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piece of Elisp so easily was really fun, so I decided to tackle
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something bigger.
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It is not rare that I need to compile and run a single C file. Nothing
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fancy, no libraries, no makefile, just a single C file to compile and
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run. I searched around the internet like "Emacs compile and run C", but
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couldn't find anything. I had been doing this by opening a shell in
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Emacs and compiling/running the program, but again, why not automate
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it?
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The code that follows is not really good. "It works" is as good as it
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gets really, and actually considering that this is the first
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substantial Elisp I have written, that is pretty impressive -for the
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language and Emacs, which are both very helpful and powerful- I think.
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```commonlisp
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(require 's)
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(defun compile-run-buffer ()
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"Compile and run buffer."
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(interactive)
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(let* ((split-file-path (split-string buffer-file-name "/"))
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(file-name (car (last split-file-path)))
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(file-name-noext (car (split-string file-name "[.]")))
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(buffer-name (concat "compile-run: " file-name-noext))
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(buffer-name* (concat "*" buffer-name "*")))
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(make-comint buffer-name "gcc" nil "-Wall" "-Wextra" "-o" file-name-noext file-name)
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(switch-to-buffer-other-window buffer-name*)
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(set-process-sentinel (get-buffer-process (current-buffer))
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(apply-partially
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'(lambda (prog-name proc even)
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(if (s-suffix? "finished\n" even)
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(progn
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(insert "Compilation successful.\n\n")
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(comint-exec (current-buffer) prog-name (concat "./" prog-name) nil nil))
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(insert (concat "Compilation failed!\n" even))))
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file-name-noext))))
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```
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Again, the code is not really good. I'm uploading it here right now
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because I'm actually very excited that I wrote this. Just now I can
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think of ways to improve this, for example moving the compiler and the
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flags to variables so that they can be customized. I could also
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improve the presentation, because strings printed by this function,
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comint and the running programs mixes up. I'll update this blog post
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if I get to updating the code.
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If this is your first time hearing about Emacs, this post may look
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very confusing. I don't to Emacs any justice here, so do check it out
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somewhere like [Emacs rocks](http://emacsrocks.com/). On the other
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hand, if you have been looking a functionality like this, hope this
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helps. If you have any suggestions about the code, I'd love to hear
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them, you can find my email on the "about me" page. Anyway, have a
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good day!
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