Question

I’m beginning to play with Clojure a bit and my Java experience is pretty limited. I’m coming from the dynamic world of Ruby and OO, so the functional side of things is very interesting!

Anyway, as I discover libraries and various tools for use (and the tutorial files for the Pragmatic Clojure Book), everything typically calls for placing files in the CLASSPATH in order for Clojure to see the library for use.

Is there such thing as good CLASSPATH practice? Would I ever want to only have a CLASSPATH with just the external libraries of files I need or can I go ahead toss any library or file I would ever need in a directory and simply define it as my CLASSPATH and only require what’s needed?

If it helps, I’m an OSX and Emacs user (Using slime and swank-clojure).

Answer 1

Personally, I’m using a variant of a clojure-project elisp function by Phil Hagelberg, see source in this post to the Clojure group. It sets up the classpath appropriately for the project you’ll be working on, then launches SLIME. (EDIT: You’ll need to change the value which gets assigned to swank-clojure-jar-path to point to clojure.jar. I’m using (expand-file-name "~/.clojure/clojure.jar") as the default.)

To answer the question about having everything on the classpath all the time vs only throwing in what’s needed: to the best of my knowledge, nothing will actually break if you take the first approach (I know I do that for experimental purposes), but apparently things might break with the first approach (see cjstehno’s comment below) and in a proper project I find the second to be cleaner. At some point it’ll be necessary to determine what libs are being used (and which versions of them), if only to tell leiningen (or maven) about it — why not keep tabs on it as you go.