HelgeSverre/sema

<p align="center"> <img src="https://raw.githubusercontent.com/helgesverre/sema/main/assets/logo.png" alt="Sema" width="640"> </p> <p align="center"> A Lisp with first-class LLM primitives, implemented in Rust. </p> <p align="center"> <a href="https://sema.run"><img src="https://img.shields.io/badge/try_it-sema.run-c8a855?style=flat" alt="Playground"></a> <a href="https://sema-lang.com/docs/"><img src="https://img.shields.io/badge/docs-sema--lang.com-c8a855?style=flat" alt="Docs"></a> <a href="https://github.com/HelgeSverre/sema/releases/latest"><img src="https://img.shields.io/github/v/tag/HelgeSverre/sema?label=version&color=c8a855&style=flat" alt="Version"></a> <a href="LICENSE"><img src="https://img.shields.io/badge/license-MIT-c8a855?style=flat" alt="License"></a> </p>

Sema is a Scheme-like Lisp where prompts are s-expressions, conversations are persistent data structures, and LLM calls are just another form of evaluation. It combines a Scheme core with Clojure-style keywords (:foo), map literals ({:key val}), and vector literals ([1 2 3]).

What It Looks Like

A coding agent with file tools, safety checks, and budget tracking — in ~40 lines:

;; Define tools the LLM can call
(deftool read-file
  "Read a file's contents"
  {:path {:type :string :description "File path"}}
  (lambda (path)
    (if (file/exists? path) (file/read path) "File not found")))

(deftool edit-file
  "Replace text in a file"
  {:path {:type :string} :old {:type :string} :new {:type :string}}
  (lambda (path old new)
    (file/write path (string/replace (file/read path) old new))
    "Done"))

(deftool run-command
  "Run a shell command"
  {:command {:type :string :description "Shell command to run"}}
  (lambda (command) (:stdout (shell "sh" "-c" command))))

;; Create an agent with tools, system prompt, and spending limit
(defagent coder
  {:system (format "You are a coding assistant. Working directory: ~a" (sys/cwd))
   :tools [read-file edit