# Yo

A work-in-progress, multi-paradigm compiled programming language designed to be simple for a large language model to write and easy for a person to read, aiming for performance within about 15% of C.

Yo is a general-purpose compiled language whose syntax is inspired by Lisp's S-expressions, intended to be simple enough for both humans and LLMs to work with. Its feature set includes first-class types, compile-time evaluation, homoiconicity and metaprogramming, closures, and algebraic effects and handlers implemented as one-shot delimited, tail-resumptive continuations.

Concurrency is handled through a built-in `Io` effect with async/await, backed by stackless coroutines and cooperative multitasking with lazy futures and multi-await. Foreign function calls use `c_include`/`extern` forms that evaluate to module values. Memory safety is the default: user code cannot cause undefined behavior without an explicit unsafe opt-in, and an `unsafe-report` command audits any unsafe surface in a project.

Reference-counted values use non-atomic counting with thread-local cycle collection, and the language supports thread-per-core parallelism. It also has a formal-verification layer, with contracts and refinement types proved at compile time against a pinned build of the Z3 solver.

Website: https://shd101wyy.github.io/Yo/