Struct Env 

pub struct Env(/* private fields */);

The runtime environment: a chain of positional frames.

A frame is a plain Vec<Value>, and a compiled variable reference is a (depth, index) pair resolved at compile time — walk depth parents, index the vector. There are no names here at all: the compiler’s scope stack is 1:1 with this chain (it pushes exactly where a frame is created), so every local is a static coordinate.

RefCell because let rec back-patches its siblings into a shared frame one at a time: the frame is created pre-sized with placeholders and filled in order, and a closure that captured it sees the later fills.

Implementations

impl Env

pub fn root() -> Env

The empty root frame every program runs in.

pub fn child(&self, slots: Vec<Value>) -> Env

Push a frame holding slots, in the order the compiler assigned them.

pub fn slot(&self, depth: u16, index: u16) -> Value

Read the local at (depth, index).

pub fn set_slot(&self, depth: u16, index: u16, value: Value)

Overwrite the local at (depth, index) — let rec’s back-patch.

Trait Implementations

impl Clone for Env

fn clone(&self) -> Env

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Env

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

Formats the value using the given formatter.