Targets · Rust · Example

Example

The whole language in one short program — a module with a record, a tagged union, a function with per-platform native bodies, and a function that wires up state, a write-back and a return — and the complete Rust it renders to. It is the same program shown on the language page.

How a Program becomes Rust, in parts. Start with the introduction, then follow each part into the rendered output and the runtime it links against.

Introduction — what the Rust target is, and how to read the rest of this section.
Capabilities — which high-level features are possible, built in or through a crate.
Example — a full program using every keyword, and the Rust it renders to.
Naming considerations — how Program's dotted names are carried into Rust.
Entry point — starting a program from main with its drivers.
Drivers — the native drivers that provide the interface, console and network.
Runtime — the Reactive and Context machinery the rendered code links against.
Native modules — the hand-written Rust behind NATIVE functions.
Keywords — how each of Program's keywords renders to Rust.
Project setup — the files and commands to build and run the rendered program.
Reserved words — the words Rust keeps for itself, and how a colliding name is escaped.

Every keyword, in one program

Each keyword has its own page under keywords; here they are all together.

MODULE App

  TYPE Profile
    FIELD Text name
    FIELD Maths.Integer age

  TYPE Status
    OPTION App.Profile active
    OPTION Text pending

  FUNCTION Text Greet
    INPUT Text name
    NATIVE js    "return 'Hi ' + name;"
    NATIVE dart  "return 'Hi ' + name;"
    NATIVE rust  "format!(\"Hi {}\", name)"

  FUNCTION Text Welcome
    INPUT BINDING App.Profile profile
    HOLE Text row
      INPUT Text line
    STATE Maths.Integer count = 0
    STATE LOCKED Network.Web.Response saved = null
    REVERSE App.Profile submit
      LET Network.Web.Response response = Network.Web.Client.Post profile
      SET saved = response
    LET Text label = Maths.Integer.ToString count
    = label

(The function's swift row is replaced with a rust one here, since Rust needs its own NATIVE body.)

Rendered Rust

The module is a mod; the record is a struct and the union an enum, both keeping their :: path; state uses generics; the function's rust body is spliced in; closures are boxed; and the trailing = is the final expression.

pub mod app {

    #[derive(Clone)]
    pub struct Profile {
        pub name: String,
        pub age: i64,
    }

    pub enum Status {
        Active(Profile),
        Pending(String),
    }

    pub fn Greet(name: String) -> String {
        format!("Hi {}", name)               // the rust NATIVE body
    }

    pub fn Welcome(profile: Profile, row: Box<dyn Fn(String) -> ReactiveValue<String>>) -> ReactiveValue<String> {
        let count = Program::_Runtime::Reactive::state::<i64>(0);
        let saved = Program::_Runtime::Reactive::state_locked::<network::web::Response>(None);
        Program::_Runtime::Reactive::reverse(submit, Box::new(move || {
            let response = network::web::client::Post(profile);
            Program::_Runtime::Reactive::set(saved, response);  // SET
        }));
        let label = maths::integer::ToString(count);
        label
    }
}

Reading it

Indentation becomes nested boxed closures — the REVERSE body is a Box::new(move || { … }). Dotted names stay real through nested modules, with :: for the dots (network::web::client::Post) — see naming considerations. The per-keyword mapping is on keywords.

Example

Contents

Every keyword, in one program

Rendered Rust

Reading it