Struct Environment 

pub struct Environment { /* private fields */ }

An environment frame (variable bindings)

Corresponds to OpenJade’s environment frames in Interpreter.

Lexical Scoping

Each frame has:

• bindings: Variables defined in this frame
• parent: Enclosing scope (None for global environment)

Variable lookup walks up the parent chain until found or global reached.

Implementations

impl Environment

pub fn new_global() -> Gc<Self>

Create a new global (top-level) environment

pub fn extend(parent: Gc<Environment>) -> Gc<Self>

Create a new child environment extending the given parent

Used for:

• Function calls (parameters in new scope)
• let, let*, letrec bindings
• Internal defines

pub fn define(&self, name: &str, value: Value)

Define a variable in this environment (set binding)

Mutates the current frame.

Used for:

• define expressions
• Function parameter bindings
• let bindings

DSSSL Note

DSSSL is mostly functional, but define at top-level is imperative. Internal defines in lambda bodies create a new frame.

pub fn lookup(&self, name: &str) -> Option<Value>

Look up a variable in this environment or any parent

Returns None if variable is undefined.

Walks up the parent chain until:

• Variable found → return value
• Global reached and not found → return None

Corresponds to OpenJade’s Interpreter::lookup().

pub fn set(&self, name: &str, value: Value) -> Result<(), String>

Set an existing variable (mutation)

Returns Ok(()) if variable found and updated, Err if not found.

Used for:

• set! expressions

R4RS vs DSSSL

R4RS allows set! on any variable. DSSSL restricts mutation (mostly functional). For now, we allow it (OpenJade does).

pub fn is_defined(&self, name: &str) -> bool

Check if a variable is defined in this environment or any parent

pub fn parent(&self) -> Option<Gc<Environment>>

Get the parent environment (if any)

pub fn local_bindings(&self) -> Vec<(Rc<str>, Value)>

Get all bindings in this frame (not including parents)

Used for debugging and introspection.

Trait Implementations

impl Clone for Environment

fn clone(&self) -> Environment

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Environment

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

Formats the value using the given formatter.

impl Drop for Environment

fn drop(&mut self)

Executes the destructor for this type.

impl Finalize for Environment

fn finalize(&self)

impl Trace for Environment

unsafe fn trace(&self)

Marks all contained Gcs.

unsafe fn root(&self)

Increments the root-count of all contained Gcs.

unsafe fn unroot(&self)

Decrements the root-count of all contained Gcs.

fn finalize_glue(&self)

Runs Finalize::finalize() on this object and all contained subobjects