Clerk

Moldable Live Programming for Clojure

🎪 View Demos • 📖 Book of Clerk 👩‍🎨 Using Clerk • 🪚 Development

Clerk takes a Clojure namespace and turns it into a notebook:

🎪 Demos

Clerk comes with a demo repo full of interesting use cases. Check them out and feel free to add your own via PRs.

⚖️ Rationale

Computational notebooks allow arguing from evidence by mixing prose with executable code. For a good overview of problems users encounter in traditional notebooks like Jupyter, see I don't like notebooks and What’s Wrong with Computational Notebooks? Pain Points, Needs, and Design Opportunities.

Specifically Clerk wants to address the following problems:

Less helpful than my editor
Notebook code being hard to reuse
Reproduction problems coming from out-of-order execution
Problems with archival and putting notebooks in source control

Clerk is a notebook library for Clojure that aims to address these problems by doing less, namely:

no editing environment, folks can keep using the editors they know and love
no new format: Clerk notebooks are either regular Clojure namespaces (interspersed with markdown comments) or regular markdown files (interspersed with Clojure code fences). This also means Clerk notebooks are meant to be stored in source control.
no out-of-order execution: Clerk notebooks always evaluate from top to bottom. Clerk builds a dependency graph of Clojure vars and only recomputes the needed changes to keep the feedback loop fast.
no external process: Clerk runs inside your Clojure process, giving Clerk access to all code on the classpath.

🚦 Status

ALPHA, expect breaking changes.

👩‍🎨 Using Clerk

To use Clerk in your project, add the following dependency to your deps.edn:

{:deps {io.github.nextjournal/clerk {:mvn/version "0.12.707"}}}

Require and start Clerk as part of your system start, e.g. in user.clj:

(require '[nextjournal.clerk :as clerk])

;; start Clerk's built-in webserver on the default port 7777, opening the browser when done
(clerk/serve! {:browse? true})

;; either call `clerk/show!` explicitly
(clerk/show! "notebooks/rule_30.clj")

;; or let Clerk watch the given `:paths` for changes
(clerk/serve! {:watch-paths ["notebooks" "src"]})

;; start with watcher and show filter function to enable notebook pinning
(clerk/serve! {:watch-paths ["notebooks" "src"] :show-filter-fn #(clojure.string/starts-with? % "notebooks")})

You can then access Clerk at http://localhost:7777.

See the /notebooks folder in the Clerk repository for a number of sample notebooks.

Editor Workflow

For even better flow states, we recommend you bind clerk/show! to a shortcut in your favorite editor:

Emacs

In Emacs, add the following to your config:

(defun clerk-show ()
  (interactive)
  (when-let
      ((filename
        (buffer-file-name)))
    (save-buffer)
    (cider-interactive-eval
     (concat "(nextjournal.clerk/show! \"" filename "\")"))))

(define-key clojure-mode-map (kbd "<M-return>") 'clerk-show)

IntelliJ/Cursive

In IntelliJ/Cursive, you can set up REPL commands via:

going to Tools→REPL→Add New REPL Command, then
add the following command: (show! "~file-path");
make sure the command is executed in the nextjournal.clerk namespace;
lastly assign a shortcut of your choice via Settings→Keymap

Neovim + Conjure

With neovim + conjure one can use the following vimscript function to save the file and show it with Clerk:

function! ClerkShow()
  exe "w"
  exe "ConjureEval (nextjournal.clerk/show! \"" . expand("%:p") . "\")"
endfunction

nmap <silent> <localleader>cs :execute ClerkShow()<CR>

🪚 Developing Clerk

Make sure you have Babashka installed, and run:

bb dev :browse\? true

The will start everything needed to develop Clerk and open your default browser. You can connect your favorite editor to it using nREPL.

Any trailing arguments to bb dev will be forwarded to clojure -X and clerk/serve!. So if you prefer to not open your browser, leave out the :browse\? true arguments.

🐞 Known Issues

See notebooks/onwards.md.

larsen/clerk