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Documentation Index

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CLS is a modern programming language designed for modular, safe, cross-platform development. It ships with a complete toolchain: the clx development CLI for building, type-checking, and running scripts, and clxr, the lightweight runtime for executing packaged .clsapp applications. CLS features static type inference, generic types, async/await coroutines, a JSX-like markup syntax called CMX, and a sandboxed virtual filesystem — all from a single Rust-powered interpreter.

Installation

Build CLS from source with Cargo and get the clx and clxr binaries ready.

Quickstart

Create your first CLS project, write a Hello World, and run it in minutes.

Language Guide

Explore CLS syntax, the type system, functions, classes, and modules.

CLI Reference

Full reference for every clx and clxr command and flag.

Standard Library

Built-in intrinsics plus math, json, async, fs, and http modules.

Embedding CLS

Integrate cls-core and cls-runtime into your own Rust application.

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What makes CLS different

Static Type Checker

Run clx check to catch type errors before execution. Supports generics, union types, literal types, and null safety — all without a compilation step.

Async / Await

First-class coroutine support with async function and await. Compose concurrent tasks with async.all() and async.race().

CMX Markup

A native JSX-like syntax for describing component trees and structured data directly in CLS source — no external template engine needed.

Virtual Filesystem

Access files through protocol URIs (app://, user://, tmp://, res://) for portable, sandboxed I/O across desktop and packaged environments.

LSP Server

clx lsp starts a Language Server Protocol server for real-time diagnostics, completions, hover docs, and go-to-definition in any LSP-compatible editor.

Embeddable Runtime

The cls-core and cls-runtime Rust crates can be embedded in any Rust application to add CLS as a scripting language with a custom module resolver.

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Get started in three steps

1

Build from source

Clone the repository and compile the toolchain with Cargo:
git clone https://github.com/elfrask/cls
cd cls
cargo build --release
The clx and clxr binaries appear in target/release/.
2

Create a project

Use clx new to scaffold a new CLS project:
clx new my-app
cd my-app
This creates cls.json and src/main.clsx with a starter main function.
3

Run your code

Execute the entry point defined in cls.json:
clx run
Pass -- followed by arguments to forward them to main(args).
CLS requires Rust (edition 2021, version 1.70+) and Cargo. No other system dependencies are needed for the core runtime.

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