Project layout

White does not require a manifest for a small program. wlc starts from one entry file and follows its imports, so a one-file project is simply:

hello/
└── main.wl

Build it from the project directory:

wlc main.wl

The executable is written beside main.wl unless -o selects another path. For a project which produces several files, keeping outputs in a separate directory avoids mixing generated artifacts with source:

wlc src/main.wl -o build/app

The build directory must already exist.

More than one source file

Local White files use an explicit .wl suffix in imports:

hello/
├── main.wl
└── greeting.wl

greeting.wl

func message(name: String) -> String {
    return "hello, " + name;
}

main.wl

import "greeting.wl"

func main() -> Int {
    print(greeting.message("White"));
    return 0;
}

An ordinary module import creates a namespace from the file name. Imports are local to the source file which declares them: importing greeting.wl inside another module does not make greeting visible everywhere else.

Paths are resolved from the importing file, not from whichever directory happened to start wlc. This keeps a project working when the compiler is run from another directory.

Directory packages

A directory becomes a package by providing _pkg.wl. That file defines the public shape of the package:

hello/
├── main.wl
└── model/
    ├── _pkg.wl
    └── user.wl

model/user.wl

class User {
    let name: String;

    init(name: String) {
        self.name = name;
    }
}

model/_pkg.wl

import User from "user.wl"

main.wl

import "model"

func main() -> Int {
    let user: model.User = model.User("White");
    print(user.name);
    return 0;
}

Inside _pkg.wl, a named import re-exports that symbol through the package. import * from "file.wl" re-exports all public symbols, while a normal import "file.wl" preserves the child module namespace. Ordinary source files do not re-export their own imports.

Names beginning with __ are private and cannot be imported through a module or package boundary.

Standard-library imports

Standard packages and files are found under WL_PATH/std and omit the .wl suffix:

import "file"
import "json"
import "strings"
import "sys"

This differs from a local file import such as import "parser.wl". The suffix makes it clear that the path names a source file rather than a standard module or directory package.

builtin, the standard Error type, and Dict support are connected to the prelude. Code may use their unqualified names without an import. An explicit import "builtin" is still valid when a qualified call such as builtin.print(...) is wanted.

std/internal is reserved for the implementation of the standard library, user projects cannot import it.