Interactive Common Lisp: An Enhanced REPL
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I created this because sometimes I want more than rlwrap but less than emacs. icl aims to hit that middle sweet spot.It's a terminal application with context-aware auto-complete, an interactive object inspector, auto-indentation, syntax colouring, persistent history, and much more. It uses sly to communicate with the child lisp process and aims to be compatible with any sly-supporting implementation. I hope others find it useful!
HN · launched Dec 14, 2025 · 101 upvotes (top 10%) · 0 views
Niche: developer command-line tools · 226 launches, 5 in the last 7 days ▼ -67% · Explore this niche →
Category and tags
- Horizontal
- Dev tools
- Developer
- Not AI
- Hobby / open-source project
Visit website ↗ Source listing ↗
More like this: all 226 launches in developer command-line tools →
Could you build this?
Partial While terminal UIs can be scaffolded, building a stable, interactive Lisp REPL that communicates via Sly/Swank protocols, handles complex Common Lisp reader macros, and manages live runtime introspection requires deep Lisp internals expertise.
What it would actually take: The architecture involves a TUI library (e.g., in Go with Bubbletea, or Common Lisp with cl-charms) connecting over sockets to a Slynk/Swank backend server running in an SBCL process. The hard part is managing asynchronous protocol communication with Slynk, parsing Lisp forms accurately for interactive completion/indentation, and cleanly handling SBCL debugger breaks and signals in the terminal.
Discussion
9 comments analyzed.
Competitors mentioned: cl-repl, Allegro IDE, LispWorks IDE, Slime, rlwrap
Concerns raised: Installation/connection issues with Slynk/Swank servers, Pasting code with long lines doesn't work well, Lacks interactive debugger (only backtrace command), Missing reverse-search-history and history-search-backward keyboard shortcuts, Slower launch time compared to alternatives
Feature requests: Add reverse-search-history (C-r) and history-search-backward (M-p) keyboard shortcuts, Improve paste handling for multi-line code, Add interactive debugger capabilities
Competitors
Other products that read as similar to this one : 42 launches clear the similarity bar, closest 8 shown.
Attention rank: #7 of 43 (itself plus its competitors, highest first, normalized so YC and Product Hunt are compared fairly).
Launched 39 days after the earliest competitor.
- Turbo Lisp · hn · 2026-10-15 · 5 upvotes · similarity 0.46
- Julius, a New Lisp Implementation · hn · 2026-05-03 · 14 upvotes · similarity 0.44
- Ced · hn · 2026-05-07 · 5 upvotes · similarity 0.43
- A Common Lisp implementation in development · hn · 2026-04-05 · 7 upvotes · similarity 0.43
- An implementation of Common Lisp in development, reached version 1.6 · hn · 2026-05-12 · 27 upvotes · similarity 0.41
- miso · github · 2026-11-04 · 52 upvotes · similarity 0.40
- I wrote a technical history book on Lisp · hn · 2026-02-17 · 252 upvotes · similarity 0.40
- I forced Claude to play Tetris in Emacs · hn · 2026-04-11 · 13 upvotes · similarity 0.39
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