December 16, 2025
Parentheses and popcorn
Show HN: Interactive Common Lisp: An Enhanced REPL
Lisp fans torn: slick new console, rough installs
TLDR: ICL is a new, feature-packed console for Common Lisp. Reactions split between hype and hiccups: install errors spark gripes, while a debate rages over no interactive debugger versus simpler tools for newcomers.
Common Lisp just got a shiny new toy: ICL, an enhanced console (“REPL”) that lets you type code, see results, and keep going. It packs modern goodies like multi-line input, saveable history, tab-completion, quick docs, object peeks, tracing, and simple comma commands. It even talks to multiple Lisp engines through Slynk, the chat line between the frontend and the language. The repo dropped with prebuilt packages and a from-source path for the brave.
The crowd reaction? Split. One camp is buzzing to try it, while others hit a wall. User dcassett’s install saga on Debian 12 ended with the ominous “Failed to connect to Slynk after 10 seconds,” then a freeze. Cue the classic HN chorus: is it my setup, the packaging, or the tool?
Then came the philosophy fight. Commenter vindarel compared ICL to cl‑repl and flagged a missing interactive debugger, adding they actually prefer that for newcomers. Instantly, it’s team “less is friendlier” versus team “give me all the gears.” Meanwhile vjust rolled in with pure hype: “awesome, I will try it.” People joked about counting parentheses and “press comma for power,” as the thread ping‑ponged between excitement and setup drama. The verdict: promising, polarizing, and Lisp.
Key Points
- •ICL is a modern, terminal-based enhanced REPL for Common Lisp with readline-style editing, persistent history, and tab completion.
- •It supports multiple Lisp implementations (SBCL, CCL, ECL, CLISP, ABCL, Clasp) and provides features like documentation lookup, object inspection, tracing, and source location.
- •Pre-built RPM and DEB packages are available via GitHub Releases; building from source requires SBCL, ocicl, and libfixposix-devel.
- •ICL offers rich command sets (navigation, documentation, inspection, macros, debugging, session) and maintains history variables for recent results and inputs.
- •ICL acts as a frontend communicating with a backend Lisp process over the Slynk protocol (from SLY), enabling consistent features and remote connections.