Luma

A small, statically-typed programming language with clear syntax and kind error messages.

void main() {
    print("Hello, Luma!");
}

This is the archived reference implementation (a0.1) — a Rust-based tree-walking interpreter. The rewrite in Luma itself (luma-lang/) is the active project. This repo is kept as a historical reference.

---

Why Luma?

Luma was built by someone who struggles to write code independently due to disabilities affecting reading, mathematics, focus, and cognitive load. Working with AI tools made building a language possible — but it also made clear how important predictable, explicit design is.

Luma is for anyone who finds programming languages overwhelming. It won't surprise you. It won't judge you. It'll tell you exactly what went wrong and how to fix it.

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Getting Started

Install

Clone and build with Cargo:

git clone https://github.com/dylanisaiahp/luma
cd luma
cargo build --release
cp target/release/luma ~/.local/bin/luma

Usage

luma new myproject        # Create a new project
luma create source/mymod  # Create a .lm file with module declaration
luma create source/mydir/ # Create a directory
luma run                  # Run from luma.toml entry point
luma run main.lm          # Run a specific file
luma build                # Compile to native binary
luma check main.lm        # Check for errors without running
luma run --time           # Show execution time
luma run --debug all      # Debug output

Project Structure

myproject/
├── source/
│   └── main.lm
├── luma.toml
└── README.md

[project]
name = "myproject"
version = "0.1.0"
description = ""
entry = "source/main.lm"

---

Examples

Hello World

void main() {
    print("Hello, Luma!");
}

Functions

int add(int x, int y) {
    return x + y;
}

void main() {
    print(add(3, 4));   # 7
}

Control Flow

void main() {
    for i in range(1, 6) {
        if i % 2 == 0 {
            print("&{i} is even");
        }
    }
}

Error Handling

worry(int) safe_divide(int a, int b) {
    if b == 0 {
        raise "cannot divide by zero";
    }
    return a / b;
}

void main() {
    int result = safe_divide(10, 2) else e {
        print(e);
        return;
    }
    print(result);
}

Structs

struct Point {
    int x;
    int y;

    int sum() {
        return x + y;
    }
}

void main() {
    Point p = Point(x: 3, y: 7);
    print(p.x);       # 3
    print(p.sum());   # 10
}

Multi-file Projects

Every importable file must declare its module name at the top:

# source/greet.lm
module greet;

string greet(string name) {
    return "Hello, &{name}!";
}

# source/main.lm
use greet;

void main() {
    print(greet("Luma"));
}

---

Error Messages

Luma tries to tell you exactly what went wrong and how to fix it:

[E010] Error: Type mismatch: expected int, got string
   ╭─[ main.lm:3:15 ]
   │
 3 │     int x = "hello";
   │             ───────
   │                ╰── Make sure the value type matches the variable declaration.
───╯

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Known Limitations

Match expression freeze in multi-module projects

The match expression can freeze when used in complex multi-module projects with many match arms (e.g., 41+ arms). This is due to scope management issues in the interpreter's function call handling when deeply nested across modules.

Workaround: Avoid match expressions in the bootstrap interpreter for now. Use if/else chains instead. This limitation will be fixed once Slate (the language being bootstrapped) can compile itself.

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License

MIT — see LICENSE.