Now that I am learning Clojure, I need to have a properly configured environment for Clojure development.

With Clojure, Emacs is the de-facto standard editor.

I've been using Emacs for a long time, but in that time I've only scratched the surface of the powerful features that are available.

My usual workflow consists of basic commands like open-file (C-x C-f), save-buffer (C-x C-s), save-buffers-kill-emacs (C-x C-c), and copy-paste. I also like to use the isearch-forward command (C-s) and the query-replace command (M-%). I've recently started using goto-line (M-g g).

I still have a long way to go to become a real Emacs nerd.

Clojure and Emacs

My Emacs skills have stagnated in recent years. When I program in Scala, I use the Scala IDE for Eclipse. When I program in Java, I use IntelliJ IDEA at work, and Eclipse for personal projects. I mostly only use Emacs for Python and C programming.

There is an excellent guide to using Clojure with Emacs in one of the chapters of Clojure for the Brave and True. This guide is based on an existing emacs configuration created by the author.

Since I already have my own Emacs configuration, and my goal is to learn both Emacs and Clojure, I've decided to update my own repository to keep it compatible with the requirements of the book.

Managing Emacs packages

My .emacs.d directory is loosely based on another one that I found on Github. I stripped out almost everything except for the structure of the project, and the init.el file. I also kept the init-elpa.el file (renamed to init-melpa.el, since I'm using MELPA, and I don't know the difference).

MELPA (Milkypostman's ELPA or Milkypostman's Experimental Lisp Package Archive) seems to be the most widely used Emacs package repository archive. So far, I have found every package I need there.

The init-melpa.el file is key because it bootstraps the package installation process by accessing the online package archive. It also contains one other important piece, which is a function called require-package. This will check if a given package is already installed, if its contents need to be refreshed, and if the package-install command should be run. This turns out to be much easier and more portable than manually running package-install on every new machine that uses the config.

(defun require-package (package &optional min-version no-refresh)
  "Install given PACKAGE, optionally requiring MIN-VERSION.
If NO-REFRESH is non-nil, the available package lists will not be
re-downloaded in order to locate PACKAGE."
  (if (package-installed-p package min-version)
      t
    (if (or (assoc package package-archive-contents) no-refresh)
        (package-install package)
      (progn
        (package-refresh-contents)
        (require-package package min-version t)))))

With this infrastructure in place, I was able to create the configuration for the major modes that I will most commonly use. I have tuareg mode for OCaml, ensime for Scala, markdown-mode for editing Markdown, and of course, clojure-mode.