fun

fun is an experimental programming language compiler/interpreter written in OCaml.

The current implementation is built around core_tt, a dependently typed core with bidirectional elaboration, normalization by evaluation, implicit arguments, nominal ADTs, structural records/modules, pattern matching, traits, algebraic effects, mutable references, and a hygienic enforestation-based macro system.

dune build
dune test
dune exec fun            # REPL

Consistency > Flexibility > Correctness.

• Consistency: one construct for many roles (struct = record / module / namespace), types are values, and the core type system carries the language model directly.
• Flexibility: willing to trade theoretical properties such as parametricity for practical power. Type-case on open Type is acceptable.
• Correctness: still valued through bidirectional checking, normalization, unification, and regression tests — but not at the expense of the language's practical shape.

The pipeline is a single path from surface syntax to values:

source → Raw_syntax → Enforest → Expand + Lower → Surface.t → Elaborate → Core.term → NbE → value

• CLAUDE.md — how to work in this repo: build/test, source layout, conventions, and recurring gotchas.
• docs/STATUS.md — canonical snapshot of what is built. When another doc disagrees on completion status, STATUS wins.
• docs/wayfinder/ — the direction map: what has been decided, what is still open (tickets), and what is still fog. Start at the Fun compiler design map. This is also where the design detail for every completed direction lives (under topics/), plus the macro-system reference library (macro-system/).