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
inline display of images
persistent REPL history
powerful REPL history browser
highly customizable REPL prompt
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 rogue 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.
When you’re done with a REPL you can dispose of it with C-c C-q.
|Avoid killing REPL buffers with C-c C-k. This will forgo some of the operations needed to properly dispose of a REPL buffer.
Normally Clojure REPLs load the following code in the first REPL that you start:
(clojure.core/apply clojure.core/require clojure.main/repl-requires)
CIDER does this as well, but goes one step further and actually allows you
to control what code to evaluate when a REPL is being initialized via
This initialization code is auto-loaded only in the first REPL namespace
user), but you can easily invoke it in any namespace using the REPL
require-repl-utils. The functionality is also accessible via
CIDER’s menu ("REPL → Require REPL utils").
You’ll rarely need the REPL utility functions when using CIDER, as it
provides many Emacs commands that behave similarly (e.g. instead of doing
(doc str) you’d probably use the
cider-doc (C-c C-d C-d) command).
Performance can degrade when the REPL buffer grows very large. This is
especially true if either
nrepl-log-messages are enabled.
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.
You can use
either clear the result of the previous evaluation, or with a prefix argument
clear the entire REPL buffer. You can also set
which will enable trimming the buffer automatically after each evaluation. This
trimming can also be invoked manually with