Dyon is designed to be used with Rust only, but not designed to replace Rust. It complements Rust on some areas where Rust has lacking features.

• It uses no garbage collector, but instead uses a lifetime checker
• For simple game and interactive programming environments
• A simple object model to make introspection and reflection easy

Because Dyon uses a simple object model, the values must be converted when talking with Rust.

See functions example

A more complex example is the dyon_interactive library.

Functions that helps talking with Rust

• dyon::embed::obj_field
• Runtime::pop
• Runtime::push
• Runtime::pop_vec4
• Runtime::push_vec4
• Runtime::var
• Runtime::expected

External functions

Example:

fn say_hello(_: &mut Runtime) -> Result<(), String> {
    println!("hi!");
    Ok(())
}

To use it with Dyon, it must be registered with a name and type information:

module.add(Arc::new("say_hello".into()), say_hello, PreludeFunction {
        lts: vec![], // lifetime constraints
        tys: vec![], // type constraints
        ret: Type::Void // return type
    });

If any arguments are mutated, add pattern (mut,_,_,...) to the function name.

For example, if 2 of 2 arguments are mutable to function foo, you register foo(mut,mut).

Mutating a variable on the stack

When mutating a variable on the stack, you need to resolve the reference first. This is because

let ind = rt.stack.pop().expect("There is no value on the stack");
let id = if let Variable::Ref(id) = rt.stack[ind] {
    id
} else {
    rt.stack[ind]
};
if let Variable::Array(ref mut arr) = rt.stack[id] {
    // mutate array here
}