Getting Started

Rue is in early development and there are no binary releases yet. You build the compiler from source. The repository bootstraps its own build tools, so this is less work than it sounds.

Prerequisites

Dotslash, which downloads and runs the pinned Buck2 build tool and Rust toolchain.
clang, used as the system linker on platforms where Rue's internal linker is not used.

Everything else comes with the repository. The first build downloads what it needs.

Building the compiler

git clone https://github.com/rue-language/rue
cd rue
scripts/rue build

The first build takes a few minutes. Later builds are fast.

scripts/rue is a small wrapper around the build system. It is the easiest way to use the compiler while you work through this tutorial, and it works from any directory inside the repository.

Running a program

Try the checked-in setup smoke test:

scripts/rue exec examples/welcome.rue

You should see 1, 2, 3, and 42 on separate lines, and the command should exit with status 0. scripts/rue exec builds the compiler if needed, compiles the source file to a temporary executable, runs it, and passes the program's exit status through. That is the whole edit-run loop for the next several chapters.

Using the compiler directly

When you want to keep the executable, ask the wrapper for the compiler's path and tell the compiler where the standard library lives:

RUE="$(scripts/rue-bin)"
export RUE_STD_PATH="$PWD/std"

"$RUE" examples/welcome.rue -o welcome
./welcome

Both lines of setup matter. scripts/rue-bin prints the absolute path of the compiler binary. RUE_STD_PATH points the compiler at the repository's std directory; scripts/rue exec sets it for you, but a direct invocation does not, and a program that imports the standard library fails without it:

error: [E0705]: standard library not found
  = help: set RUE_STD_PATH to the toolchain's standard-library directory

The rest of this tutorial assumes RUE and RUE_STD_PATH are set whenever it shows a direct compiler command.

Running tests

Rue has a built-in test runner. Once you have a file with tests in it (chapter 13), run them with:

"$RUE" test main.rue

Targets

Rue produces native executables for x86-64-linux, aarch64-linux, and aarch64-macos. Cross-target machine-code emission is available, but producing a runnable executable for another platform may require that platform's system tools.

If you work on the compiler

Most people should stay with scripts/rue. If you are changing the compiler itself, you will also meet the lower-level Buck2 commands, for example ./buck2 build root//crates/rue:rue. docs/development.md in the repository covers that workflow.

That's it. In the next chapter you'll write your first program.