hedit

a terminal text editor written in hica

hedit editing source code in a terminal

Overview

hedit is a lightweight terminal text editor written entirely in hica. It combines familiar editor behaviour with the language features I wanted to exercise in a real application: algebraic effects, immutable data structures, pattern matching, native compilation through Koka, and an embedded scripting language.

I built it because I wanted an editor of my own, but also because a compiler needs a demanding user. A terminal editor brings input decoding, screen rendering, mutable-looking state, file and clipboard access, undo history, configuration, plugins, and recovery into one compact system. That makes hedit both a tool I can use and an end-to-end integration workload for hica.

Features

Familiar keybindings, readline-style motions, incremental search, and system clipboard integration.
Multiple buffers, vertical and horizontal split panes, syntax highlighting, and mouse support.
Multi-cursor editing with simultaneous, offset-aware text changes.
A branching visual undo tree that preserves edits made after an undo.
Session and crash recovery for buffers, pane layouts, cursors, and unsaved scratch content.
A searchable command palette with shell command execution.
Configuration, keybindings, and plugins written in HiLisp.

Effects at the Boundary

The editor core is mostly pure. An incoming event is resolved to an Action, and that action produces a new EditorState. Terminal and clipboard operations sit behind hica algebraic effects, so the same event loop can run against a real terminal or a scripted test handler:

effect Terminal {
  fun poll_event() : Event
  fun render_frame(buf: ScreenBuffer)
  fun get_dimensions() : (int, int)
  fun set_cursor_style(style: CursorStyle)
}

effect Clipboard {
  fun get_selection() : string
  fun set_selection(text: string)
}

Undo history uses a named Buffer effect. Each open buffer gets an isolated handler containing its own branching revision tree, while the text buffer itself remains a plain value that pure editing functions can transform and tests can inspect.

Scriptable with HiLisp

hedit embeds HiLisp, a small Lisp interpreter also written in hica. The same runtime handles settings, keybindings, and plugins:

;; ~/.config/hedit/init.hl
(set "tabsize" 4)
(set "theme" "ilseon")

(bind "Ctrl-s" 'save)
(bind "Meta-w" 'close-buffer)

(plugin "greeter")

Plugins can subscribe to editor lifecycle hooks, inspect buffer statistics, cancel selected actions, and return status messages without gaining unrestricted access to mutate editor state.

Install

hicurl https://github.com/cladam/hedit/releases/latest/download/install.sh | sh

Or, if you haven’t tried hicurl yet…

curl -fsSL https://github.com/cladam/hedit/releases/latest/download/install.sh | sh

Pre-built binaries are available for macOS ARM64 and Linux ARM64/x86_64. The installer also installs the hedit(1) man page.