Struct Engine 

pub struct Engine { /* private fields */ }

The persistent embedding entry point. Holds the table of registered host functions and compiles scripts into reusable Programs.

This is the library analogue of the one-shot [crate::candela_run]: it does not run a script and hand back stdout, it keeps compiler + VM state resident so the host can call into the script repeatedly.

Implementations

impl Engine

pub fn new() -> Self

pub fn register_host_fn<Marker, F>(&mut self, namespace: &str, name: &str, f: F)

where F: IntoHostFn<Marker>,

Registers a typed host function under namespace.name.

The closure may take any combination of i64/i32, f64, bool, String (or a single &str) arguments and return one of those or (). The declared types are checked against the script’s host block when Engine::compile runs; a mismatch is a clean Diagnostic, never a panic.

pub fn register_host_fn_variadic<F>( &mut self, namespace: &str, name: &str, f: F, )

where F: Fn(&[Value]) -> Value + 'static,

Registers a variadic host function under namespace.name.

Unlike Engine::register_host_fn, the closure receives every argument as a &[Value] slice of any length and returns a single Value, so arguments of mixed / dynamically-typed shape can cross the boundary without a fixed Rust signature. The host block must declare the function with a ... argument list:

host "app" {
    log(...);
}

No arity or per-argument type checking is performed at the call site; the closure interprets the slice it is handed. A non-variadic declaration bound to a variadic closure (or vice versa) is a clean Diagnostic at Engine::compile time.

pub fn compile(&self, src: &str, filename: &str) -> Result<Program, Diagnostic>

Compiles src into a reusable Program, binding every host function it declares to the matching registered closure.

main is executed once here (module instantiation), so any top-level setup runs before the host makes its first Program::call.

Errors

Returns a Diagnostic if the script fails to parse/type-check, if a declared host function has no registered closure, if a registered closure’s arity/types disagree with the host block, or if running main raises a runtime error.

Trait Implementations

impl Default for Engine

fn default() -> Engine

Returns the “default value” for a type.