I often find myself browsing the Internet and then suddenly I want to have a Clojure REPL at my fingertips. As I’ve become better with emacs and paredit I’ve become dependent on the powerful editing this combo affords. The rest of this post details how I changed my five step process into a two step process. It does not explain basic emacs/slime setup but rather explains how I cut a few steps out of a suboptimal workflow for getting a powerful Clojure REPL up and running in emacs.
My previous workflow was the following:
- Open a terminal
- Change to the root of Clojure project where I use Leiningen and have swank-clojure as a dependency.
- Run the command
- Start emacs
This five step process was terrible. From me seeing something interesting to try to having a REPL open took too much time.
Today I changed my process so it on takes two steps. They are:
- Start emacs
This is a much better. I’ll admit had a lot of room for improvement so it wasn’t too hard to make it better. Below are the steps I took to cut three steps.
First, using Leiningen 1.4.0, I ran
lein install swank-clojure 1.3.0-SNAPSHOT. This installed a script called swank-clojure into $HOME/.lein/bin. When run, this script starts a swank server waiting for connections on port 4005.
Next I wrote a function in elisp that gives emacs the ability to call the newly installed swank-clojure script, wait for the swank server to start, and then connect to it. This function,
clojure-swank, can be seen below. It creates a buffer named
*clojure-swank*, runs the newly installed script, and captures the output in the freshly created buffer. When the “Connection opened” line appears
slime-connect is called, connecting emacs to the freshly started swank server. After this we are at the REPL with all the advantages that emacs and paredit give us.
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I’ve also written a
clojure-kill-swank function for stopping the swank server.
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Both of those functions need to be added to a location where they will get defined on emacs start-up. Once this is done the powerful REPL you are used to emacs providing can be at your finger tips in practically no time at all.