Visibility and Modules

Run uses a simple module system: each file is a module and each directory is a package. Visibility is controlled by the pub keyword.

Private by default

Everything in Run is private by default. Only items marked with pub are accessible from other packages.

math/vector.run

pub type Vec3 struct {
    pub x: f64
    pub y: f64
    pub z: f64
}

// public — callable from other packages
pub fun (v @Vec3) length() f64 {
    return math.sqrt(v.x*v.x + v.y*v.y + v.z*v.z)
}

// private — only visible within the math package
fun normalize_internal(v: &Vec3) {
    len := v.length()
    v.x = v.x / len
    v.y = v.y / len
    v.z = v.z / len
}

Files and packages

A single .run file is a module. All files in the same directory belong to the same package and can access each other’s private items.

myproject/
    main.run          // package main
    math/
        vector.run    // package math
        matrix.run    // package math — can see vector.run's private items
    net/
        http.run      // package net

Using packages

Import a package with use and access its public items through the package name.

package main

use "math"
use "fmt"

pub fun main() {
    v := math.Vec3{ x: 1.0, y: 2.0, z: 3.0 }
    fmt.println(v.length())
}

This system is deliberately simple. There are no complex visibility modifiers or nested module hierarchies — just pub or private, at the package boundary.