Modules

Rue programs can be split across files. A file imports another file with @import("path.rue"), binds the returned module object to a name, and then uses that name to access public declarations.

A Two-File Program

Create a directory named lib, then create lib/math.rue:

pub fn double(x: i32) -> i32 {
    x * 2
}

fn secret() -> i32 {
    99
}

Then create main.rue next to the lib directory:

const math = @import("lib/math.rue");

fn main() -> i32 {
    math.double(21)
}

Compile and run it:

RUE="$(scripts/rue-bin)"
"$RUE" main.rue -o main
./main
echo $?  # prints: 42

@import("lib/math.rue") loads the other file and returns a module object. The const math = ... binding gives that module object a local name.

Public and Private Declarations

Across directory boundaries, only declarations marked pub are available through a module object. In the example above, math.double(21) works because double is public.

This does not compile:

const math = @import("lib/math.rue");

fn main() -> i32 {
    math.secret()
}

For the cross-directory import used above, secret is private to lib/math.rue, so the compiler reports that the function is private. Use pub only for declarations that are part of the imported file's interface.

Import Paths

Relative import paths are resolved from the importing file's directory:

const math = @import("lib/math.rue");

The path string must be a string literal known at compile time. Rue does not dynamically load modules at runtime; imports are part of compilation.

Standard Library Status

Rue's accepted standard-library direction is an explicit standard module:

const std = @import("std");

The intent is that standard-library types and functions are accessed through that namespace, for example std.option.Option or std.arraybuf.ArrayBuf.

The repository wrapper commands know where the checked-in std/ directory lives. If you invoke the compiler binary directly from somewhere else and see standard library not found, set RUE_STD_PATH to the repository's std directory.

The important habit is still the same: use explicit module imports and namespace-qualified access rather than hidden global names.

Next Steps

You've learned the current core of Rue. For the complete language reference, read the Language Specification.

Rue is still in early development. If you find bugs or have ideas, please file an issue.