Struct HostFn 

pub struct HostFn { /* private fields */ }

A host function: a native callback provided by the embedder, behind the Rc a Value::HostFn carries.

It includes a name, arity, and code. The evaluator gathers arguments according to arity before calling the function, making it strict and curried.

Ctx is passed to allow the callback to call Elly functions (apply_with) using the same ID source, preventing identity collisions for minted closures.

Arity must be at least 1; zero-argument constants are supplied as values.

Implementations

impl HostFn

pub fn new( name: impl Into<Text>, arity: usize, f: impl Fn(&[Value], &Ctx) -> Result<Value, Raised> + 'static, ) -> HostFn

A host function taking arity arguments.

Name is for diagnostics; identity is the allocation. Panics on arity == 0.

pub fn name(&self) -> &Text

The name the function renders under.

pub fn arity(&self) -> usize

How many arguments it is called with.

Trait Implementations

impl Debug for HostFn

The callback is not Debug, so the derive cannot apply; the shape a Value::HostFn shows is its name and arity, which is what identifies it in a dump anyway.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.