# litto

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Lightweight building blocks for implementing interpreters in Rust. Ideally for DSL use-cases.

## Exmaple Languages

- **tinylang**: A tiny language with S-exp syntax. It basically only implements `lambda` without even primitive types like bools, ints, or lists. Note [those types can  be built using `lambda`](src/tinylang/tests.rs).
- **minilang**: Extends tinylang with a richer standard library and types. Run `cd examples/minilang-repl; cargo run` to try it in an REPL.

## Goals

- **Simple**. The code should be simple to reason about.
- **Powerful**. Use simple concepts to express powerful features. For example, lambda can be easily implemented and it is pretty powerful.
- **Easy-to-use**.
  - Sharing data and functions between Rust and the DSL is easy and safe.
  - The DSL can easily opt-in a [garbage colletor](https://github.com/quark-zju/gcmodule) to make memory management easier.
- **Flexible**. Things like syntax, AST internal representation, standard library functions, types, how to resolve a name, what is a function, and how to call a function, are all customizable.
- **Rust**. This library is written in Rust and solves Rust problems. Not intened to be used in other languages via FFI.

## Non-goals

- **Performance**. Performance is a best-effort within the simplicity constraint. Practically, performance-critical code should be in native Rust.
- **Features**. Feature-complete is not a goal, especially when it conflicts with simplicity.
  - **Stackless**. The Rust language natively uses the native stack when calling a function. Therefore a stackless is not simple in Rust. This means things like co-routine and `call/cc` are not out-of-box.
  - **Multi-Thread**. Right now it's not a goal because the gc library does not support it.