side effects?

src/run.rs

@@ -6,22 +6,9 @@ use crate::{
 };
 
 #[derive(Clone)]
-pub struct Function {
-	name: String,
-	inner: Rc<dyn Fn(Vec<Value>) -> Value>,
-}
-
-impl Function {
-	pub fn new(name: String, func: impl Fn(Vec<Value>) -> Value + 'static) -> Self {
-		Self {
-			name,
-			inner: Rc::new(func),
-		}
-	}
-
-	pub fn call(&self, args: Vec<Value>) -> Value {
-		(self.inner)(args)
-	}
+struct Function {
+	name: &'static str,
+	inner: Rc<dyn Fn(&mut Scope, Vec<Value>) -> Value>,
 }
 
 impl Debug for Function {
@@ -33,7 +20,7 @@ impl Debug for Function {
 #[derive(Debug, Clone, Default)]
 pub struct Scope {
 	variables: HashMap<String, ValueInner>,
-	functions: HashMap<String, Function>,
+	functions: HashMap<&'static str, Function>,
 }
 
 impl Scope {
@@ -49,9 +36,18 @@ impl Scope {
 		}
 	}
 
-	pub fn add_fn(&mut self, name: &'static str, f: impl Fn(Vec<Value>) -> Value + 'static) {
-		self.functions
-			.insert(name.into(), Function::new(name.into(), f));
+	pub fn add_fn(
+		&mut self,
+		name: &'static str,
+		f: impl Fn(&mut Scope, Vec<Value>) -> Value + 'static,
+	) {
+		self.functions.insert(
+			name,
+			Function {
+				name: name,
+				inner: Rc::new(f),
+			},
+		);
 	}
 }
 
@@ -95,10 +91,11 @@ impl Eval for Expression {
 			Expression::Constant(inner) => inner.eval(scope),
 			Expression::Variable(inner) => inner.eval(scope),
 			Expression::Call { callee, args } => {
-				let Some(function) = scope.functions.get(callee).cloned() else {
+				let Some(function) = scope.functions.get(callee.as_str()).cloned() else {
 					panic!("attempt to call non-existent function {callee}")
 				};
-				function.call(args.into_iter().map(|arg| arg.eval(scope)).collect())
+				let args = args.into_iter().map(|arg| arg.eval(scope)).collect();
+				(function.inner)(scope, args)
 			}
 		}
 	}
@@ -197,7 +194,7 @@ mod tests {
 	#[test]
 	fn test_call() {
 		let mut scope = Scope::default();
-		scope.add_fn("sqr", |args| {
+		scope.add_fn("sqr", |_, args| {
 			let [arg] = args.as_slice() else {
 				panic!("exactly one argument expected");
 			};