We have blocks & scopes

src/interpret.rs

@@ -31,12 +31,16 @@ macro_rules! some_or_error {
 	}
 }
 
-fn get_value(v: Value, scope: &HashMap<String, VarType>) -> Result<TeaValue, InterpreterError> {
+fn get_value(v: Value, scopes: &mut [Scope]) -> Result<TeaValue, InterpreterError> {
 	match v {
 		Value::Lit(t) => Ok(t),
-		Value::Id(s) => match scope.get(&s) {
-			None => Err(InterpreterError::new("undefined variable")),
-			Some(VarType::Const(t)) => Ok(t.clone()),
+		Value::Id(s) => {
+			match scopes.iter().rev().skip_while(|scope| !scope.contains_key(&s)).next() {
+				None => Err(InterpreterError::new("undefined variable")),
+				Some(scope) => match scope.get(&s).unwrap() {
+					VarType::Const(t) => Ok(t.clone()),
+				},
+			}
 		},
 	}
 }
@@ -58,20 +62,28 @@ macro_rules! apply_op {
 	}
 }
 
-pub fn interpret(ast: Vec<ASTNode>) -> Result<Vec<Value>, InterpreterError> {
+type Scope = HashMap<String, VarType>;
+
+fn interpret_block(ast: Vec<ASTNode>, scopes: &mut Vec<Scope>) -> Result<Vec<Value>, InterpreterError> {
 	let mut ast = ast.clone();
 	ast.reverse();
 	let mut stack = vec![];
-	let mut global_scope: HashMap<String, VarType> = HashMap::new();
+	//let mut scope = Scope::new();
 	loop {
 		match ast.pop() {
 			None => return Ok(stack),
+			Some(ASTNode::Block(tokens)) => {
+				scopes.push(HashMap::new());
+				let mut result = interpret_block(tokens, scopes)?;
+				scopes.pop();
+				stack.append(&mut result);
+			},
 			Some(ASTNode::Val(v)) => stack.push(v),
 			Some(ASTNode::BinOp(op)) => {
 				let b = some_or_error!(stack.pop(), InterpreterError::new("right value needed"));
 				let a = some_or_error!(stack.pop(), InterpreterError::new("left value needed"));
-				let b: TeaValue = get_value(b, &global_scope)?;
-				let a: TeaValue = get_value(a, &global_scope)?;
+				let b: TeaValue = get_value(b, scopes)?;
+				let a: TeaValue = get_value(a, scopes)?;
 				stack.push(Value::Lit(match op {
 					Operator::Plus => {
 						apply_op!(a, b, +)
@@ -89,7 +101,7 @@ pub fn interpret(ast: Vec<ASTNode>) -> Result<Vec<Value>, InterpreterError> {
 			},
 			Some(ASTNode::UnaryMinus) => {
 				let x = some_or_error!(stack.pop(), InterpreterError::new("value needed"));
-				let x: TeaValue = get_value(x, &global_scope)?;
+				let x: TeaValue = get_value(x, scopes)?;
 				stack.push(Value::Lit(match x {
 					TeaValue::Float(f) => TeaValue::Float(-f),
 					TeaValue::Int(i) => TeaValue::Int(-i),
@@ -100,14 +112,15 @@ pub fn interpret(ast: Vec<ASTNode>) -> Result<Vec<Value>, InterpreterError> {
 			Some(ASTNode::ConstDecl) => {
 				let rhs = some_or_error!(stack.pop(), InterpreterError::new("rhs value needed"));
 				let lhs = some_or_error!(stack.pop(), InterpreterError::new("lhs value needed"));
-				let rhs: TeaValue = get_value(rhs, &global_scope)?;
+				let rhs: TeaValue = get_value(rhs, scopes)?;
+				//let current_scope = .unwrap();
 				match lhs {
 					Value::Lit(_) => return Err(InterpreterError::new("invalid left hand side")),
 					Value::Id(s) => {
-						if global_scope.contains_key(&s) {
+						if scopes.last().unwrap().contains_key(&s) {
 							return Err(InterpreterError::new("already defined constant"));
 						} else {
-							global_scope.insert(s, VarType::Const(rhs));
+							scopes.last_mut().unwrap().insert(s, VarType::Const(rhs));
 						}
 					}
 				}
@@ -120,3 +133,8 @@ pub fn interpret(ast: Vec<ASTNode>) -> Result<Vec<Value>, InterpreterError> {
 		}
 	}
 }
+
+pub fn interpret(ast: Vec<ASTNode>) -> Result<Vec<Value>, InterpreterError> {
+	let mut scopes = vec![HashMap::new()];
+	interpret_block(ast, &mut scopes)
+}

src/lex/keyword.rs

@@ -3,6 +3,7 @@ use super::{ whitespace_chars, Token };
 #[derive(Debug)]
 pub enum Keyword {
 	Let,
+	Fn,
 }
 
 macro_rules! match_keyword {
@@ -15,5 +16,6 @@ macro_rules! match_keyword {
 
 pub fn parse_keyword(input: &str) -> Option<(Token, &str)> {
 	match_keyword!("let", Token::Kw(Keyword::Let), input);
+	match_keyword!("fn", Token::Kw(Keyword::Fn), input);
 	None
 }

src/lex/symbol.rs

@@ -4,6 +4,8 @@ use super::Token;
 pub enum Symbol {
 	EqualSign,
 	Semicolon,
+	OpenBrace,
+	CloseBrace,
 }
 
 pub fn parse_symbol(input: &str) -> Option<(Token, &str)> {
@@ -12,6 +14,8 @@ pub fn parse_symbol(input: &str) -> Option<(Token, &str)> {
 	match c {
 		'=' => Some((Token::Sym(Symbol::EqualSign), input)),
 		';' => Some((Token::Sym(Symbol::Semicolon), input)),
+		'{' => Some((Token::Sym(Symbol::OpenBrace), input)),
+		'}' => Some((Token::Sym(Symbol::CloseBrace), input)),
 		_ => None
 	}
 }

src/parse.rs

@@ -20,6 +20,7 @@ pub enum ASTNode {
 	BinOp(Operator), // binary operation
 	UnaryMinus,
 	StatementEnd,
+	Block(Vec<ASTNode>),
 }
 
 #[derive(Debug)]
@@ -55,9 +56,28 @@ macro_rules! assert_match {
 
 fn next_expr_end(tokens: &[Token]) -> usize {
 	let mut index = 0;
+	let mut block_count = 0usize;
 	loop {
-		if matches!(tokens.get(index), Some(Token::Sym(Symbol::Semicolon)) | None) {
-			return index;
+		match tokens.get(index) {
+			Some(Token::Sym(Symbol::OpenBrace)) => block_count += 1,
+			Some(Token::Sym(Symbol::CloseBrace)) => block_count -= 1,
+			Some(Token::Sym(Symbol::Semicolon)) if block_count == 0 => return index,
+			None => return index,
+			_ => (),
+		}
+		index += 1;
+	}
+}
+
+fn next_block_end(tokens: &[Token]) -> Result<usize, ParseError> {
+	let mut index = 0;
+	loop {
+		let token = tokens.get(index);
+		if token.is_none() {
+			return Err(ParseError::new("} expected"));
+		}
+		if matches!(token, Some(Token::Sym(Symbol::CloseBrace))) {
+			return Ok(index);
 		}
 		index += 1;
 	}
@@ -82,10 +102,31 @@ fn parse_expr(tokens: &[Token]) -> Result<(Vec<ASTNode>, usize), ParseError> {
 				ast.push(ASTNode::ConstDecl);
 				index += count + 3; // 4 + count - 1
 			},
+			Some(Token::Kw(Keyword::Fn)) => {
+				/*let id = match_or_return!(tokens.get(index + 1), Token::Id(a), a, ParseError::new("identifier expected after 'let' keyword"));
+				match_or_return!(tokens.get(index + 2), Token::Sym(Symbol::EqualSign), (), ParseError::new("= expected after identifier"));
+				let tokens = &tokens[(3 + index)..];
+				let next_end = next_expr_end(tokens);
+				let (mut expr, count) = parse_expr(&tokens[..next_end])?;
+				ast.push(ASTNode::Val(Value::Id(id.to_owned())));
+				ast.append(&mut expr);
+				ast.push(ASTNode::ConstDecl);
+				index += count + 3; // 4 + count - 1*/
+				todo!()
+			},
+			Some(Token::Sym(Symbol::EqualSign)) => todo!(),
+			Some(Token::Sym(Symbol::OpenBrace)) => {
+				let end = next_block_end(&tokens[(index + 1)..])?;
+				let (expr, count) = parse_expr(&tokens[(index + 1)..(index + end + 1)])?;
+				ast.push(ASTNode::Block(expr));
+				index += count + 1;
+			},
+			Some(Token::Sym(Symbol::CloseBrace)) => {
+				return Err(ParseError::new("unexpected }"));
+			},
 			Some(Token::Sym(Symbol::Semicolon)) => {
 				ast.push(ASTNode::StatementEnd);
 			},
-			Some(Token::Sym(Symbol::EqualSign)) => todo!(),
 			Some(Token::Op(op)) => {
 				if ast.is_empty() && matches!(op, Operator::Minus) {
 					ast.push(match tokens.get(index + 1) {

test.tea

@@ -0,0 +1,8 @@
+
+let x = 5;
+let y = {
+	let x = 1;
+	x + 1
+};
+x + y
+