Yo

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.