Hammock Editor

A terminal text editor for deep thinking. Inspired by Rich Hickey's Hammock Driven Development. Minimal C kernel. Clojure scripting. Markdown-native.

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What It Is

Hammock is a Clojure-oriented terminal editor inspired by Emacs, but it's not Emacs. It's built for people who think in Clojure and write in GitHub-flavored Markdown.

The *scratch* buffer runs Clojure, evaluated by SCI (Small Clojure Interpreter) compiled as a native shared library via GraalVM. You can modify editor behavior live with C-j.

Architecture

Two layers: a functional core in Clojure and an imperative shell in C. Commands return effect vectors describing what C should do, rather than doing it directly.

C Kernel: src/

Performance-critical primitives: ncurses display, gap buffer text storage, key input, in-process SCI calls, and cursor movement.

Clojure Layer: clj/

Everything else: commands, keybindings, modes, editor state via atoms, git integration, markdown navigation, and buffer management.

Effect Vectors

Clojure commands return data like [:message "saved"] or [:point-forward 1]. C interprets and executes them.

Live Reload

Atom watches on keybindings, commands, and modes propagate changes instantly. swap! takes effect on the next loop iteration.

How It Works

Initialize the C kernel

ncurses terminal, input handling, gap buffers

Load Clojure modules via SCI

In-process evaluation of clj/*.clj through libsci

Fetch keybinding and mode tables

Clojure exports EDN, C parses it into its keymap

Enter the main loop

Each keystroke dispatches through the keymap. Hot-path commands run in C for zero latency. Everything else round-trips through Clojure.

Commands in Clojure

All editor commands are defined in Clojure using defcommand and return effect vectors:

;; clj/commands.clj
(defcommand "save-buffer"
  "Save the current buffer to disk"
  (fn []
    [(fx/save-buffer)
     (fx/message "Buffer saved.")]))

(defcommand "git-status"
  "Show git status in a buffer"
  (fn []
    (let [status (git/status)]
      [(fx/switch-to-buffer "*git-status*")
       (fx/insert status)])))

Features

Gap buffer text storage
Clojure scripting via SCI
GitHub-flavored Markdown mode
Git integration (status, diff, commit, log)
Incremental search
Window splitting
Live Clojure evaluation with C-j
Buffer list management
Syntax highlighting (C, Clojure, Bash, Markdown)
Emacs-style keybindings
PTY-based shell in a buffer
Claude Code integration
Help system (describe-key, describe-function, apropos)
Hot-reloadable configuration

Build

Requires a C11 compiler, ncurses, and GraalVM CE with native-image (provided by the Nix flake).

$ nix develop

$ make -C libsci

$ make

Built by Tobi Lehman