Introduction

Rasmalai is a systems language with one radical promise: every value is freed at a point you can see in the source. No garbage collector pausing your program, no borrow checker negotiating with you, no manual free to forget. A scope ends, its values drop — deterministically, on the same thread, with zero pause.

Everything else follows from that promise:

One static binary (rnx) covers editing, running, testing, formatting, and shipping.
Native 64-bit types everywhere — Int is always 64 bits, Float is always IEEE-754 double. No platform surprises.
Four backends, one semantics — interpreter, Cranelift JIT, LLVM, and AOT binaries all run the same code the same way.

Install the toolchain

Everything ships in one binary:

curl -fsSL https://rnx.dev/install.sh | sh

The script detects your OS and CPU and places rnx in ~/.local/bin (%LOCALAPPDATA%\rnx\bin on Windows). Confirm it:

rnx --version

Your first program

Scaffold a project and run it:

rnx init hello
cd hello
rnx run

text

Hello from hello!

The scaffold created two things: a Project.config manifest and src/main.rnx. Open the source file:

.rnx

fn Main(): Int {
    print("Hello from hello!");
    return 0;
}

The scaffold uses a named Main entry point and greets you with the project name. Top-level statements with no wrapper work too — that is the shape used for the rest of this page.

Three ideas are packed in here, and they recur everywhere:

The entry file runs top-level statements directly — no main wrapper needed. A top-level return <Int> sets the process exit code (0 means success); falling through returns 0. An explicit fn main(): Int / fn Main(): Int still works when you want it.
print() writes its arguments separated by spaces, then a newline. It works identically on every backend, which is why this guide uses it instead of a debugger.
Blocks use curly braces and statements need no semicolons. If you have written Go, Rust, or TypeScript, your fingers already know the way.

Try changing it — add a second line and run again:

.rnx

let name = "ore";
print("hello,", name);
print("2 + 2 =", 2 + 2);

rnx run executes through the interpreter in milliseconds. When you want a real binary instead, rnx build --release compiles through LLVM and links a stripped native executable with the same output.

Note

You will see fn Main(): Int (capital M) in some reference pages. Both spellings compile, and both are optional: top-level statements run as-is in files, in rnx run, and in the browser playground. Top-level await works there too.

Check without running

rnx check parses and typechecks without generating code. It finishes in milliseconds, which makes it the command you will reach for most while editing:

rnx check

text

Checked hello (ok)

Now break something on purpose — delete a brace — and run rnx check again. The diagnostic names an error code, points at the exact column, and suggests a fix. Every error in Rasmalai looks like this, and the codes are documented in the Language Manual.

Where to go next

This guide walks you from zero to productive in nine short chapters:

Basics and Types — bindings, 64-bit numbers, strings, operators.
Control Flow — branches, loops, switch, and defer.
Functions and Closures — signatures, lambdas, and defaults.
Data Structures — structs, classes, records, enums.
Collections — arrays, maps, sets, and functional transforms.
Error Handling — null and T?, Result, throws, try/catch.
Modules and Packages — imports, the standard library, manifests.
AI Assistants & MCP — connect agents and harnesses through rnx mcp.
Troubleshooting & Reinstall — read diagnostics, fix breakage, reinstall cleanly.

Coming from another language? Jump to your Rosetta guide for side-by-side translations. Want exact semantics instead of stories? The Language Manual is the normative reference.

Basics and Types