CIDER comes with a powerful REPL that complements the interactive
development functionality in
cider-mode. Using the CIDER REPL you
can experiment with your running program, test functions, or just
explore a new library you're interested in using. The CIDER REPL offers a number of advanced features:
- font-locking (the same as in
- quick access to many CIDER commands (e.g. definition and documentation lookup, tracing, etc)
- pretty-printing of evaluation results
- eldoc support
- highly customizable REPL prompt
Interacting with the REPL
Interacting with CIDER's REPL is pretty simple - most of the time you'd just write expressions there and press RET to evaluate them.
But the REPL is a bit more powerful than that and it allows you to do some things that might not be available in other Clojure REPLs. Some examples of such things would be:
- You can close an incomplete expression with C-Ret
- You can enter a multi-line expression by pressing C-j at the end of each line
- You can quickly jump to the definition of a symbol (.) or to its documentation (C-c C-d d)
- You can clear the output of the last expression with C-c C-o
- You can clear the REPL buffer with C-u C-c C-o
- You can jump between your source buffers and the REPL with C-c C-z
- You can jump between your Clojure and ClojureScript REPLs with C-c M-o
On top of this the REPL is extremely configurable and you can tweak almost every aspect of it.
If you accidentally try to evaluate something that's going to take a lot of time (if it finishes at all), you can interrupt the rouge evaluation operation by pressing C-c C-c.
Note that this is different from the keybinding for interrupting evaluations in source buffers, namely C-c C-b.
Quitting a REPL
When you're done with a REPL you can dispose of it with C-c C-q.
Please, avoid killing REPL buffers with C-c C-k
Performance can degrade when the REPL buffer grows very large. This is
especially true if either
nrepl-log-messages are enabled. You can use
either clear the result of the previous evaluation, or with a prefix argument
clear the entire REPL buffer.
Very long lines are guaranteed to bring Emacs to a crawl, so using a value of
cider-print-fn that wraps lines beyond a certain width (i.e. any of the
built-in options except for
pr) is advised.