R2ND Docs

Everything you need to build with the R2ND ecosystem — from installation to shipping a full UI app.

Reference Documentation

Complete language spec — types, control flow, structs, enums, traits, generics, FFI, memory management, and more.

Introduction

R2ND stands for "Road to No Dependencies" — a self-hosted ecosystem built entirely from scratch. Custom language, UI framework, renderer, package manager — all with zero external dependencies.

At the core is M++, a compiled language that emits LLVM IR and produces native binaries via clang. The toolchain, standard library, and every layer of the stack are written from the ground up.

Pipeline: .mpp → LLVM IR → clang → native binary

Installation

The R2ND installer handles everything automatically. Download it from files.r2nd.org and run it.

# Download and run the installer
# From: https://files.r2nd.org/installers/r2nd_setup.exe

# The installer will:
#   1. Download mpp.exe (M++ compiler)
#   2. Download r2nd.exe (CLI tool)
#   3. Bundle LLVM/clang if not found
#   4. Install C++ build tools if needed
#   5. Add everything to PATH

# After install, restart your terminal:
mpp --version

LLVM & Build Tools: The installer automatically detects and bundles LLVM/clang. If Visual Studio Build Tools are missing, it installs them too.

Install scope: Supports both per-user and system-wide installation.

Quick Start

Create a new project and run it in two commands:

# Create a new project
mpp init
# Creates: mpp.toml, src/main.mpp, .mpp_packages/

# Build and run
mpp build --run

The generated src/main.mpp:

fn main() {
    print("Hello from my-project!");
}

Project Structure & Build System

mpp.toml

name = "my-app"
version = "1.0.0"
main = "src/main.mpp"
opt = "0"

[dependencies]
r2nd-ui = "0.1.0"

Commands

mpp init— Create new project

mpp build— Compile project

mpp build --run— Compile and run

mpp install <package>— Install a package

mpp <file.mpp> --llvm— Compile single file

Project layout

my-app/
├── mpp.toml          # Project config
├── src/
│   └── main.mpp      # Entry point
├── examples/         # Example files
└── .mpp_packages/    # Installed packages

Package System

# Install a package
mpp install r2nd-ui

# This downloads from files.r2nd.org/packages/
# Adds to mpp.toml [dependencies]
# Extracts to .mpp_packages/r2nd-ui/

# Use in code:
import "r2nd-ui"

M++ Language

Looking for the full reference? The complete M++ language documentation with search, 21 sections, and comprehensive examples is at M++ Language Reference →

Quick overview of the language:

Variables & Types

let name = "R2ND";
let mut count: int = 0;
let pi: float = 3.14159;
let active: bool = true;

Functions

fn add(a: int, b: int) -> int {
    return a + b;
}

fn greet(name: string) {
    print("Hello, " + name + "!");
}

Arrays & Loops

let items = ["one", "two", "three"];
let mut i = 0;
while i < len(items) {
    print(items[i]);
    i = i + 1;
}

Structs

struct Point {
    x: float,
    y: float
}

let p = Point { x: 1.0, y: 2.5 };
print(p.x);

Imports

import "utils.mpp"
import "r2nd-ui"  // package import

Built-in Functions

printinputlenpushpopto_stringto_intparse_inttrimsplitfile_readfile_writefile_existsdir_listexecallocfreegetenv

R2ND UI Framework

A complete, zero-dependency UI framework. Declare layout in R2ML (XML), wire logic in M++.

Setup

mpp init
mpp install r2nd-ui

Layout — `examples/app.r2ml`

<window width="800" height="600" bg="181825" layout="flex-col">
  <div height="48" bg="1e1e3a" layout="flex-row" padding="12">
    <label height="28" fg="a0b0ff" font-scale="2">My App</label>
    <div grow="1"></div>
    <button width="80" height="28" bg="3050c0" fg="ffffff" radius="6">Click Me</button>
  </div>
  <div grow="1" bg="1a1a2e" layout="flex-col" padding="20">
    <label height="24" fg="d0d8ff">Welcome to R2ND UI!</label>
  </div>
</window>

Logic — `src/main.mpp`

import "r2nd-ui"

let mut root: int = -1;

fn load_ui(w: int, h: int) {
    root = r2ml_load("examples/app.r2ml");
    ui_set(root, EF_W, w);
    ui_set(root, EF_H, h);
    ui_layout(root);
}

fn on_resize(w: int, h: int) {
    ui_set(root, EF_W, w);
    ui_set(root, EF_H, h);
    ui_layout(root);
}

fn on_click() {
    ui_set_text(evt_target, "Clicked!");
}

fn main() {
    let hwnd = win32_create_window("My App", 800, 600);
    win32_show_window(hwnd);
    gfx_init(800, 600);
    timer_init();
    ui_init();
    ui_events_init();
    load_ui(800, 600);

    // Bind click to all buttons
    let mut i = 0;
    while i < ui_elem_count {
        if ui_get(i, EF_TAG) == ETAG_BUTTON {
            ui_on(i, EVT_CLICK, on_click as ptr);
        }
        i = i + 1;
    }

    let msg = alloc(48);
    while win32_running {
        while (PeekMessageA(msg, null, 0u32, 0u32, 1u32) as int) != 0 {
            TranslateMessage(msg);
            DispatchMessageA(msg);
        }
        if !win32_running { break; }
        if win32_width != fb_width || win32_height != fb_height {
            gfx_resize(win32_width, win32_height);
            on_resize(win32_width, win32_height);
        }
        ui_process_events(root);
        gfx_clear(rgb(24, 24, 37));
        ui_render(root);
        gfx_present(hwnd);
        win32_clear_input();
        Sleep(1u32);
    }
    free(msg);
}

R2ML Reference

Elements

windowdivlabelbuttoninput

Attributes

widthheightbgfgborderlayoutgappaddinggrowradiusoverflowfont-scale

UI API Functions

ui_initui_events_initui_layoutui_renderui_process_eventsui_onui_setui_getui_set_textui_get_textr2ml_loadgfx_initgfx_resizegfx_cleargfx_present

CLI Reference

Command	Description
`mpp init`	Create new project with mpp.toml
`mpp build`	Build project from mpp.toml
`mpp build --run`	Build and run
`mpp install <pkg>`	Install package from files.r2nd.org
`mpp <file> --llvm`	Compile single file
`mpp <file> --llvm -q`	Compile quietly
`mpp <file> --llvm --run`	Compile and run single file
`r2nd mpp build`	Same as mpp build (via r2nd CLI)
`r2nd --version`	Show version