Struct Parameter 

pub struct Parameter { /* private fields */ }

A dynamic parameter: a named fluid binding with a fallback default.

Backed by a DynamicEnv, a parameter reads the innermost dynamic binding for its name and falls back to its default when none is active. This is the binding organ’s surface for parameterize-style rebinding.

Implementations

impl Parameter

pub fn new(name: Symbol, default: Value) -> Self

Creates a parameter over a fresh DynamicEnv with the given default.

pub fn with_dynamic_env( name: Symbol, default: Value, dynamic: DynamicEnv, ) -> Self

Creates a parameter bound to an existing DynamicEnv.

Use this to share one environment across parameters that must observe each other’s frames.

pub fn name(&self) -> &Symbol

Returns the parameter’s name.

pub fn get(&self) -> Result<Value>

Returns the current value: the innermost binding, or the default.

pub fn with_value<T>( &self, value: Value, body: impl FnOnce() -> Result<T>, ) -> Result<T>

Runs body with the parameter rebound to value for that dynamic extent.

The previous value is restored when body returns or unwinds.

Examples

use std::sync::Arc;
use sim_kernel::{Cx, DefaultFactory, NoopEvalPolicy, Symbol};
use sim_lib_binding::Parameter;

let mut cx = Cx::new(Arc::new(NoopEvalPolicy), Arc::new(DefaultFactory));
let default = cx.factory().symbol(Symbol::new("default")).unwrap();
let temporary = cx.factory().symbol(Symbol::new("temporary")).unwrap();
let parameter = Parameter::new(Symbol::new("current"), default.clone());

parameter
    .with_value(temporary.clone(), || {
        assert_eq!(parameter.get()?, temporary);
        Ok(())
    })
    .unwrap();
assert_eq!(parameter.get().unwrap(), default);

Trait Implementations

impl Clone for Parameter

fn clone(&self) -> Parameter

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Parameter

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

Formats the value using the given formatter.