Struct Scope 

pub struct Scope(pub Rc<RefCell<ScopeData>>);

A lexical environment: a table of bindings with an optional parent.

Name lookup (Scope::get) searches the scope itself and then its ancestors. New bindings (Scope::set) always go into the scope itself. A Scope is also the storage of a Value::Namespace.

Scope is a cheap handle: clones share the same bindings.

Examples

use swan_core::value::{Scope, Value};

let parent = Scope::new();
parent.set("x", Value::Numb(1.0));

let child = parent.new_child();
child.set("y", Value::Numb(2.0));

assert_eq!(child.get("x"), Value::Numb(1.0));   // inherited
assert_eq!(parent.get("y"), Value::Nothing);    // not visible upwards

Tuple Fields

0: Rc<RefCell<ScopeData>>

Implementations

impl Scope

pub fn new() -> Self

Create a top-level scope with no parent.

pub fn with_parent(parent: Scope) -> Self

Create a child scope that inherits from a parent.

pub fn new_child(&self) -> Self

Creates a new child scope using self as the parent environment.

pub fn get(&self, key: &str) -> Value

Returns the value bound to key in this scope or its nearest ancestor that binds it, or Value::Nothing if no scope binds it.

The borrow on self is released before recursing into the parent so that there is no live RefCell borrow held across the recursive call. This prevents a runtime panic in the (unlikely but possible) event that the same Scope node appears more than once in the chain.

pub fn lift(&self, key: &str) -> Value

Returns the value bound to key in the outermost scope of the chain that binds it, or Value::Nothing if no scope binds it.

This is the opposite search order of Scope::get. It implements the Swan lifting operator $name.

pub fn set(&self, key: impl Into<String>, val: Value)

Inserts or updates a binding in the current local scope only.

Trait Implementations

impl Clone for Scope

fn clone(&self) -> Scope

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Scope

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

Formats the value using the given formatter.

impl Eq for Scope

impl PartialEq for Scope

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.