add scope ops

src/run.rs

@@ -1,4 +1,4 @@
-use std::{collections::HashMap, fmt::Debug, rc::Rc};
+use std::{borrow::Cow, collections::HashMap, fmt::Debug, rc::Rc};
 
 use crate::{
 	ast::{Constant, Expression, Location},
@@ -36,6 +36,20 @@ pub struct Scope {
 	pub functions: HashMap<String, Function>,
 }
 
+impl Scope {
+	pub fn get(&self, name: impl AsRef<str>) -> Value {
+		self.variables.get(name.as_ref()).cloned()
+	}
+
+	pub fn set(&mut self, name: Cow<str>, value: Value) {
+		if let Some(value) = value {
+			self.variables.insert(name.into(), value);
+		} else {
+			self.variables.remove(name.as_ref());
+		}
+	}
+}
+
 pub trait Eval {
 	fn eval(&self, scope: &mut Scope) -> Value;
 }
@@ -54,7 +68,7 @@ impl Eval for Constant {
 impl Eval for Location {
 	fn eval(&self, scope: &mut Scope) -> Value {
 		match self {
-			Location::Variable { name } => scope.variables.get(name).cloned(),
+			Location::Variable { name } => scope.get(name),
 			Location::Field { table, index } => {
 				let table = table.eval(scope);
 				let Some(ValueInner::Table(table)) = table else {