GitHub - JeffBezanson/femtolisp: a lightweight, robust, scheme-like lisp implementation
Hacker News
February 23, 2026
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GitHub - JeffBezanson/femtolisp: A Lightweight, Robust Scheme-Like Lisp Implementation
Jeff Bezanson has developed **femtolisp**, a lightweight and robust implementation of a Scheme-like Lisp dialect. Originally conceived as an experiment to create the fastest lisp interpreter in under 1000 lines of C code, femtolisp evolved into a compact yet feature-rich language. Despite its minimal size—just 150kb—it boasts a impressive array of functionalities, including vectors, strings, gensyms, prettyprinting, hash tables, and support for using C data types directly, akin to Python's ctypes. The implementation is highly compatible with Scheme, incorporating some R6RS features, and includes a bytecode compiler and virtual machine (VM) that ensures excellent performance.
One of femtolisp's standout features is its approach to tail recursion. While many Lisp implementations shy away from proper tail calls
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Originally published on Hacker News on 2/23/2026