Implement new grammar

examples/fibonacci.ds

@@ -0,0 +1,11 @@
+fibonacci = function <i> {
+	if i <= 1 {
+		1
+	} else if i == 2 {
+		2
+	} else {
+		output (fibonacci - 1) + (fibonacci - 2)
+	}
+}
+
+(fibonacci 20)

examples/fizzbuzz.ds

@@ -1,31 +1,15 @@
-fizzbuzz_basic = function <limit> {
+count = 1
-	count = 1
 
-	while count < limit {		
+while count <= 15 {
-		if count % 3 == 0 && count % 5 == 0 {
+	(output count)
-			(output 'fizzbuzz')
-		} else f count % 3 == 0 {
-			(output 'fizz')
-		} else if count % 5 == 0 {
-			(output 'buzz')
-		} else 
-			(output count)
 
-		count += 1
+	if count % 3 == 0 {
+		(output 'fizz')
 	}
-}
-
-fizzbuzz_match <limit> {
-	count = 1
 	
-	while count < 1 {
+	if count % 5 == 0 {
-		output match [count % 3 == 0, count % 5 == 0] {
+		(output 'buzz')
-			[true, false] => 'fizz'
-			[false, true] => 'buzz'
-			[true, true] => 'fizzbuzz'
-		}
 	}
+	
+	count += 1
 }
-
-fizzbuzz_basic<15>
-fizzbuzz_match<15>

examples/hello_world.ds

@@ -0,0 +1,9 @@
+(output 'Hello, world!')
+
+main = function <message> {
+	while 1 == 1 {
+		(output message)
+	}
+}
+
+(main 'Hello dust ~*')

src/abstract_tree/assignment.rs

@@ -1,33 +1,71 @@
 use serde::{Deserialize, Serialize};
 use tree_sitter::Node;
 
-use crate::{AbstractTree, Result, Value, VariableMap};
+use crate::{AbstractTree, Error, Result, Value, VariableMap};
 
 use super::{identifier::Identifier, statement::Statement};
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub struct Assignment {
     identifier: Identifier,
+    operator: AssignmentOperator,
     statement: Statement,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
+pub enum AssignmentOperator {
+    Equal,
+    PlusEqual,
+    MinusEqual,
+}
+
 impl AbstractTree for Assignment {
     fn from_syntax_node(node: Node, source: &str) -> Result<Self> {
         let identifier_node = node.child(0).unwrap();
         let identifier = Identifier::from_syntax_node(identifier_node, source)?;
 
+        let operator_node = node.child(1).unwrap().child(0).unwrap();
+        let operator = match operator_node.kind() {
+            "=" => AssignmentOperator::Equal,
+            "+=" => AssignmentOperator::PlusEqual,
+            "-=" => AssignmentOperator::MinusEqual,
+            _ => {
+                return Err(Error::UnexpectedSyntax {
+                    expected: "=, += or -=",
+                    actual: operator_node.kind(),
+                    location: operator_node.start_position(),
+                    relevant_source: source[node.byte_range()].to_string(),
+                })
+            }
+        };
+
         let statement_node = node.child(2).unwrap();
         let statement = Statement::from_syntax_node(statement_node, source)?;
 
         Ok(Assignment {
             identifier,
+            operator,
             statement,
         })
     }
 
     fn run(&self, context: &mut VariableMap) -> Result<Value> {
         let key = self.identifier.clone().take_inner();
-        let value = self.statement.run(context)?;
+        let mut value = self.statement.run(context)?;
+
+        match self.operator {
+            AssignmentOperator::PlusEqual => {
+                if let Some(previous_value) = context.get_value(&key)? {
+                    value += previous_value
+                }
+            }
+            AssignmentOperator::MinusEqual => {
+                if let Some(previous_value) = context.get_value(&key)? {
+                    value -= previous_value
+                }
+            }
+            AssignmentOperator::Equal => {}
+        }
 
         context.set_value(key, value)?;
 

src/abstract_tree/expression.rs

@@ -1,7 +1,7 @@
 use serde::{Deserialize, Serialize};
 use tree_sitter::Node;
 
-use crate::{tool::Tool, AbstractTree, Error, Identifier, Result, Value, VariableMap};
+use crate::{AbstractTree, Error, Identifier, Result, Value, VariableMap};
 
 use super::{function_call::FunctionCall, logic::Logic, math::Math};
 
@@ -12,7 +12,6 @@ pub enum Expression {
     Math(Box<Math>),
     Logic(Box<Logic>),
     FunctionCall(FunctionCall),
-    ToolCall(Box<Tool>),
 }
 
 impl AbstractTree for Expression {
@@ -29,7 +28,6 @@ impl AbstractTree for Expression {
             "function_call" => {
                 Expression::FunctionCall(FunctionCall::from_syntax_node(child, source)?)
             }
-            "tool_call" => Expression::ToolCall(Box::new(Tool::from_syntax_node(child, source)?)),
             _ => {
                 return Err(Error::UnexpectedSyntax {
                     expected: "value, identifier, math or function_call",
@@ -50,7 +48,6 @@ impl AbstractTree for Expression {
             Expression::Math(math) => math.run(context),
             Expression::Logic(logic) => logic.run(context),
             Expression::FunctionCall(function_call) => function_call.run(context),
-            Expression::ToolCall(tool_call) => tool_call.run(context),
         }
     }
 }

src/abstract_tree/function_call.rs

@@ -1,72 +1,89 @@
 use serde::{Deserialize, Serialize};
 use tree_sitter::Node;
 
-use crate::{AbstractTree, Result, Value, VariableMap};
+use crate::{tool::Tool, AbstractTree, Result, Value, VariableMap};
 
 use super::{expression::Expression, identifier::Identifier};
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub struct FunctionCall {
-    identifier: Identifier,
+    name: FunctionName,
-    expressions: Vec<Expression>,
+    arguments: Vec<Expression>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
+pub enum FunctionName {
+    Identifier(Identifier),
+    Tool(Tool),
 }
 
 impl AbstractTree for FunctionCall {
     fn from_syntax_node(node: Node, source: &str) -> Result<Self> {
         debug_assert_eq!("function_call", node.kind());
 
-        let identifier_node = node.child(1).unwrap();
+        let name_node = node.child(1).unwrap();
-        let identifier = Identifier::from_syntax_node(identifier_node, source)?;
 
-        let mut expressions = Vec::new();
+        let name = match name_node.kind() {
+            "identifier" => {
+                FunctionName::Identifier(Identifier::from_syntax_node(name_node, source)?)
+            }
+            "tool" => {
+                let tool_node = name_node.child(0).unwrap();
+                let tool = match tool_node.kind() {
+                    "output" => Tool::Output,
+                    "read" => Tool::Read,
+                    _ => panic!(""),
+                };
+
+                FunctionName::Tool(tool)
+            }
+            _ => panic!(""),
+        };
+
+        let mut arguments = Vec::new();
 
         let mut current_index = 2;
         while current_index < node.child_count() - 1 {
             let expression_node = node.child(current_index).unwrap();
             let expression = Expression::from_syntax_node(expression_node, source)?;
 
-            expressions.push(expression);
+            arguments.push(expression);
 
             current_index += 1;
         }
 
-        Ok(FunctionCall {
+        Ok(FunctionCall { name, arguments })
-            identifier,
-            expressions,
-        })
     }
 
     fn run(&self, context: &mut VariableMap) -> Result<Value> {
-        let identifier = &self.identifier;
+        let identifier = match &self.name {
+            FunctionName::Identifier(identifier) => identifier,
+            FunctionName::Tool(tool) => {
+                let value = self
+                    .arguments
+                    .first()
+                    .map(|expression| expression.run(context))
+                    .unwrap_or(Ok(Value::Empty))?;
+
+                return tool.run(&value);
+            }
+        };
         let definition = if let Some(value) = context.get_value(identifier.inner())? {
             value.as_function().cloned()?
         } else {
             return Err(crate::Error::FunctionIdentifierNotFound(identifier.clone()));
         };
 
-        let id_expr_pairs = definition.identifiers().iter().zip(self.expressions.iter());
+        let id_expr_pairs = definition.identifiers().iter().zip(self.arguments.iter());
+        let mut function_context = context.clone();
 
         for (identifier, expression) in id_expr_pairs {
             let key = identifier.clone().take_inner();
-            let value = expression.run(context)?;
+            let value = expression.run(&mut function_context)?;
 
-            context.set_value(key, value)?;
+            function_context.set_value(key, value)?;
         }
 
-        let mut results = Vec::with_capacity(self.expressions.len());
+        definition.body().run(&mut function_context)
-
-        for item in definition.items() {
-            let result = item.run(context)?;
-
-            results.push(result);
-        }
-
-        for identifier in definition.identifiers() {
-            let key = identifier.inner();
-
-            context.remove(&key);
-        }
-
-        Ok(Value::List(results))
     }
 }

src/abstract_tree/item.rs

@@ -11,38 +11,52 @@ use crate::{AbstractTree, Error, Result, Statement, Value, VariableMap};
 /// to produce a single value or interact with a context by creating or
 /// referencing variables.
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum Item {
+pub struct Item {
-    Comment(String),
+    statements: Vec<Statement>,
-    Statement(Statement),
+}
+
+impl Item {
+    pub fn new(statements: Vec<Statement>) -> Self {
+        Self { statements }
+    }
 }
 
 impl AbstractTree for Item {
     fn from_syntax_node(node: Node, source: &str) -> Result<Self> {
         debug_assert_eq!("item", node.kind());
 
-        let child = node.child(0).unwrap();
+        let child_count = node.child_count();
+        let mut statements = Vec::with_capacity(child_count);
 
-        if child.kind() == "comment" {
+        for index in 0..child_count {
-            let byte_range = child.byte_range();
+            let child = node.child(index).unwrap();
-            let comment_text = &source[byte_range];
 
-            Ok(Item::Comment(comment_text.to_string()))
+            let statement = match child.kind() {
-        } else if child.kind() == "statement" {
+                "statement" => Statement::from_syntax_node(child, source)?,
-            Ok(Item::Statement(Statement::from_syntax_node(child, source)?))
+                _ => {
-        } else {
+                    return Err(Error::UnexpectedSyntax {
-            Err(Error::UnexpectedSyntax {
+                        expected: "comment or statement",
-                expected: "comment or statement",
+                        actual: child.kind(),
-                actual: child.kind(),
+                        location: child.start_position(),
-                location: child.start_position(),
+                        relevant_source: source[node.byte_range()].to_string(),
-                relevant_source: source[node.byte_range()].to_string(),
+                    })
-            })
+                }
+            };
+
+            statements.push(statement);
         }
+
+        Ok(Item { statements })
     }
 
     fn run(&self, context: &mut VariableMap) -> Result<Value> {
-        match self {
+        let mut prev_result = Ok(Value::Empty);
-            Item::Comment(text) => Ok(Value::String(text.clone())),
+
-            Item::Statement(statement) => statement.run(context),
+        for statement in &self.statements {
+            prev_result?;
+            prev_result = statement.run(context);
         }
+
+        prev_result
     }
 }

src/abstract_tree/logic.rs

@@ -20,6 +20,10 @@ impl AbstractTree for Logic {
             "==" => LogicOperator::Equal,
             "&&" => LogicOperator::And,
             "||" => LogicOperator::Or,
+            ">" => LogicOperator::Greater,
+            "<" => LogicOperator::Less,
+            ">=" => LogicOperator::GreaterOrEqual,
+            "<=" => LogicOperator::LessOrEqaul,
             _ => {
                 return Err(Error::UnexpectedSyntax {
                     expected: "==, && or ||",
@@ -41,15 +45,25 @@ impl AbstractTree for Logic {
     }
 
     fn run(&self, context: &mut VariableMap) -> Result<Value> {
-        let left_value = self.left.run(context)?;
+        let left = self.left.run(context)?;
-        let right_value = self.right.run(context)?;
+        let right = self.right.run(context)?;
-        let outcome = match self.operator {
+        let result = match self.operator {
-            LogicOperator::Equal => left_value == right_value,
+            LogicOperator::Equal => {
-            LogicOperator::And => left_value.as_boolean()? && right_value.as_boolean()?,
+                if let (Ok(left_num), Ok(right_num)) = (left.as_number(), right.as_number()) {
-            LogicOperator::Or => left_value.as_boolean()? || right_value.as_boolean()?,
+                    left_num == right_num
+                } else {
+                    left == right
+                }
+            }
+            LogicOperator::And => left.as_boolean()? && right.as_boolean()?,
+            LogicOperator::Or => left.as_boolean()? || right.as_boolean()?,
+            LogicOperator::Greater => left > right,
+            LogicOperator::Less => left < right,
+            LogicOperator::GreaterOrEqual => left >= right,
+            LogicOperator::LessOrEqaul => left <= right,
         };
 
-        Ok(Value::Boolean(outcome))
+        Ok(Value::Boolean(result))
     }
 }
 
@@ -58,4 +72,8 @@ pub enum LogicOperator {
     Equal,
     And,
     Or,
+    Greater,
+    Less,
+    GreaterOrEqual,
+    LessOrEqaul,
 }

src/abstract_tree/statement.rs

@@ -2,21 +2,20 @@ use serde::{Deserialize, Serialize};
 use tree_sitter::Node;
 
 use crate::{
-    r#while::While, tool::Tool, AbstractTree, Assignment, Error, Expression, IfElse, Match, Result,
+    r#while::While, AbstractTree, Assignment, Error, Expression, IfElse, Match, Result, Value,
-    Value, VariableMap,
+    VariableMap,
 };
 
 /// Abstract representation of a statement.
 ///
-/// Items are either comments, which do nothing, or statements, which can be run
+/// A statement may evaluate to an Empty value when run. If a Statement is an
-/// to produce a single value or interact with their context.
+/// Expression, it will always return a non-empty value when run.
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub enum Statement {
     Assignment(Box<Assignment>),
     Expression(Expression),
     IfElse(Box<IfElse>),
     Match(Match),
-    Tool(Tool),
     While(Box<While>),
 }
 
@@ -57,7 +56,6 @@ impl AbstractTree for Statement {
             Statement::Expression(expression) => expression.run(context),
             Statement::IfElse(if_else) => if_else.run(context),
             Statement::Match(r#match) => r#match.run(context),
-            Statement::Tool(tool) => tool.run(context),
             Statement::While(r#while) => r#while.run(context),
         }
     }

src/abstract_tree/tool.rs

@@ -1,43 +1,30 @@
-use serde::{Deserialize, Serialize};
+use std::fs::read_to_string;
-use tree_sitter::Node;
 
-use crate::{AbstractTree, Error, Expression, Result, Value, VariableMap};
+use serde::{Deserialize, Serialize};
+
+use crate::{Result, Value};
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub enum Tool {
-    Output(Expression),
+    Output,
+    Read,
 }
 
-impl AbstractTree for Tool {
+impl Tool {
-    fn from_syntax_node(node: Node, source: &str) -> Result<Self> {
+    pub fn run(&self, value: &Value) -> Result<Value> {
-        let tool_node = node.child(1).unwrap();
+        let value = match self {
-        let tool_name = tool_node.kind();
+            Tool::Output => {
+                println!("{value}");
 
-        match tool_name {
+                Value::Empty
-            "output" => {
-                let expression_node = tool_node.child(1).unwrap();
-                let expression = Expression::from_syntax_node(expression_node, source)?;
-
-                Ok(Tool::Output(expression))
             }
-            _ => Err(Error::UnexpectedSyntax {
+            Tool::Read => {
-                expected: "output",
+                let file_contents = read_to_string(value.as_string()?)?;
-                actual: tool_name,
-                location: tool_node.start_position(),
-                relevant_source: tool_node.kind().to_string(),
-            }),
-        }
-    }
 
-    fn run(&self, context: &mut VariableMap) -> Result<Value> {
+                Value::String(file_contents)
-        match self {
-            Tool::Output(expression) => {
-                let value = expression.run(context)?;
-
-                println!("{value}")
             }
-        }
+        };
 
-        Ok(Value::Empty)
+        Ok(value)
     }
 }

src/abstract_tree/while.rs

@@ -1,11 +1,11 @@
 use serde::{Deserialize, Serialize};
 
-use crate::{AbstractTree, Expression, Item};
+use crate::{AbstractTree, Expression, Item, Result, Value, VariableMap};
 
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub struct While {
     expression: Expression,
-    item: Item,
+    items: Vec<Item>,
 }
 
 impl AbstractTree for While {
@@ -15,15 +15,24 @@ impl AbstractTree for While {
         let expression_node = node.child(1).unwrap();
         let expression = Expression::from_syntax_node(expression_node, source)?;
 
-        let item_node = node.child(3).unwrap();
+        let child_count = node.child_count();
-        let item = Item::from_syntax_node(item_node, source)?;
+        let mut items = Vec::with_capacity(child_count);
 
-        Ok(While { expression, item })
+        for index in 3..child_count - 1 {
+            let item_node = node.child(index).unwrap();
+            let item = Item::from_syntax_node(item_node, source)?;
+
+            items.push(item);
+        }
+
+        Ok(While { expression, items })
     }
 
-    fn run(&self, context: &mut crate::VariableMap) -> crate::Result<crate::Value> {
+    fn run(&self, context: &mut VariableMap) -> Result<Value> {
         while self.expression.run(context)?.as_boolean()? {
-            self.item.run(context)?;
+            for item in &self.items {
+                item.run(context)?;
+            }
         }
 
         Ok(crate::Value::Empty)
@@ -36,9 +45,6 @@ mod tests {
 
     #[test]
     fn evalualate_while_loop() {
-        assert_eq!(
+        assert_eq!(evaluate("while false { 'foo' }"), Ok(crate::Value::Empty))
-            evaluate("while false { 'foo' }"),
-            vec![Ok(crate::Value::Empty)]
-        )
     }
 }

src/evaluator.rs

@@ -19,7 +19,7 @@ use crate::{abstract_tree::item::Item, language, AbstractTree, Result, Value, Va
 /// # use dust::*;
 /// assert_eq!(evaluate("1 + 2 + 3"), vec![Ok(Value::Integer(6))]);
 /// ```
-pub fn evaluate(source: &str) -> Vec<Result<Value>> {
+pub fn evaluate(source: &str) -> Result<Value> {
     let mut context = VariableMap::new();
 
     evaluate_with_context(source, &mut context)
@@ -44,7 +44,7 @@ pub fn evaluate(source: &str) -> Vec<Result<Value>> {
 ///     vec![Ok(Value::Empty), Ok(Value::Integer(10))]
 /// );
 /// ```
-pub fn evaluate_with_context(source: &str, context: &mut VariableMap) -> Vec<Result<Value>> {
+pub fn evaluate_with_context(source: &str, context: &mut VariableMap) -> Result<Value> {
     let mut parser = Parser::new();
     parser.set_language(language()).unwrap();
 
@@ -80,26 +80,17 @@ impl<'context, 'code> Evaluator<'context, 'code> {
         }
     }
 
-    fn run(self) -> Vec<Result<Value>> {
+    fn run(self) -> Result<Value> {
         let mut cursor = self.syntax_tree.walk();
         let root_node = cursor.node();
-        let item_count = root_node.child_count();
+        let mut prev_result = Ok(Value::Empty);
-        let mut results = Vec::with_capacity(item_count);
 
         for item_node in root_node.children(&mut cursor) {
-            let item_result = Item::from_syntax_node(item_node, self.source);
+            let item = Item::from_syntax_node(item_node, self.source)?;
-
+            prev_result = item.run(self.context);
-            match item_result {
-                Ok(item) => {
-                    let eval_result = item.run(self.context);
-
-                    results.push(eval_result);
-                }
-                Err(error) => results.push(Err(error)),
-            }
         }
 
-        results
+        prev_result
     }
 }
 
@@ -114,49 +105,34 @@ mod tests {
 
     #[test]
     fn evaluate_empty() {
-        assert_eq!(evaluate("x = 9"), vec![Ok(Value::Empty)]);
+        assert_eq!(evaluate("x = 9"), Ok(Value::Empty));
-        assert_eq!(evaluate("x = 1 + 1"), vec![Ok(Value::Empty)]);
+        assert_eq!(evaluate("x = 1 + 1"), Ok(Value::Empty));
     }
 
     #[test]
     fn evaluate_integer() {
-        assert_eq!(evaluate("1"), vec![Ok(Value::Integer(1))]);
+        assert_eq!(evaluate("1"), Ok(Value::Integer(1)));
-        assert_eq!(evaluate("123"), vec![Ok(Value::Integer(123))]);
+        assert_eq!(evaluate("123"), Ok(Value::Integer(123)));
-        assert_eq!(evaluate("-666"), vec![Ok(Value::Integer(-666))]);
+        assert_eq!(evaluate("-666"), Ok(Value::Integer(-666)));
     }
 
     #[test]
     fn evaluate_float() {
-        assert_eq!(evaluate("0.1"), vec![Ok(Value::Float(0.1))]);
+        assert_eq!(evaluate("0.1"), Ok(Value::Float(0.1)));
-        assert_eq!(evaluate("12.3"), vec![Ok(Value::Float(12.3))]);
+        assert_eq!(evaluate("12.3"), Ok(Value::Float(12.3)));
-        assert_eq!(evaluate("-6.66"), vec![Ok(Value::Float(-6.66))]);
+        assert_eq!(evaluate("-6.66"), Ok(Value::Float(-6.66)));
     }
 
     #[test]
     fn evaluate_string() {
-        assert_eq!(
+        assert_eq!(evaluate("\"one\""), Ok(Value::String("one".to_string())));
-            evaluate("\"one\""),
+        assert_eq!(evaluate("'one'"), Ok(Value::String("one".to_string())));
-            vec![Ok(Value::String("one".to_string()))]
+        assert_eq!(evaluate("`one`"), Ok(Value::String("one".to_string())));
-        );
+        assert_eq!(evaluate("`'one'`"), Ok(Value::String("'one'".to_string())));
-        assert_eq!(
+        assert_eq!(evaluate("'`one`'"), Ok(Value::String("`one`".to_string())));
-            evaluate("'one'"),
-            vec![Ok(Value::String("one".to_string()))]
-        );
-        assert_eq!(
-            evaluate("`one`"),
-            vec![Ok(Value::String("one".to_string()))]
-        );
-        assert_eq!(
-            evaluate("`'one'`"),
-            vec![Ok(Value::String("'one'".to_string()))]
-        );
-        assert_eq!(
-            evaluate("'`one`'"),
-            vec![Ok(Value::String("`one`".to_string()))]
-        );
         assert_eq!(
             evaluate("\"'one'\""),
-            vec![Ok(Value::String("'one'".to_string()))]
+            Ok(Value::String("'one'".to_string()))
         );
     }
 
@@ -164,11 +140,11 @@ mod tests {
     fn evaluate_list() {
         assert_eq!(
             evaluate("[1, 2, 'foobar']"),
-            vec![Ok(Value::List(vec![
+            Ok(Value::List(vec![
                 Value::Integer(1),
                 Value::Integer(2),
                 Value::String("foobar".to_string()),
-            ]))]
+            ]))
         );
     }
 
@@ -180,7 +156,7 @@ mod tests {
         map.set_value("foo".to_string(), Value::String("bar".to_string()))
             .unwrap();
 
-        assert_eq!(evaluate("{ x = 1 foo = 'bar' }"), vec![Ok(Value::Map(map))]);
+        assert_eq!(evaluate("{ x = 1 foo = 'bar' }"), Ok(Value::Map(map)));
     }
 
     #[test]
@@ -207,7 +183,7 @@ mod tests {
                 }
                 "
             ),
-            vec![Ok(Value::Table(table))]
+            Ok(Value::Table(table))
         );
     }
 
@@ -215,19 +191,16 @@ mod tests {
     fn evaluate_if_then() {
         assert_eq!(
             evaluate("if true then 'true'"),
-            vec![Ok(Value::String("true".to_string()))]
+            Ok(Value::String("true".to_string()))
         );
     }
 
     #[test]
     fn evaluate_if_then_else() {
-        assert_eq!(
+        assert_eq!(evaluate("if false then 1 else 2"), Ok(Value::Integer(2)));
-            evaluate("if false then 1 else 2"),
-            vec![Ok(Value::Integer(2))]
-        );
         assert_eq!(
             evaluate("if true then 1.0 else 42.0"),
-            vec![Ok(Value::Float(1.0))]
+            Ok(Value::Float(1.0))
         );
     }
 
@@ -244,7 +217,7 @@ mod tests {
                         'ok'
                 "
             ),
-            vec![Ok(Value::String("ok".to_string()))]
+            Ok(Value::String("ok".to_string()))
         );
     }
 
@@ -264,7 +237,7 @@ mod tests {
                     else 'ok'
                 "
             ),
-            vec![Ok(Value::String("ok".to_string()))]
+            Ok(Value::String("ok".to_string()))
         );
     }
 
@@ -272,14 +245,14 @@ mod tests {
     fn evaluate_function() {
         let function = Function::new(
             vec![Identifier::new("message".to_string())],
-            vec![Item::Statement(Statement::Expression(
+            Item::new(vec![Statement::Expression(Expression::Identifier(
-                Expression::Identifier(Identifier::new("message".to_string())),
+                Identifier::new("message".to_string()),
-            ))],
+            ))]),
         );
 
         assert_eq!(
             evaluate("function <message> { message }"),
-            vec![Ok(Value::Function(function))]
+            Ok(Value::Function(function))
         );
     }
 
@@ -295,15 +268,12 @@ mod tests {
                 ",
                 &mut context
             ),
-            vec![
+            Ok(Value::String("Hiya".to_string()))
-                Ok(Value::Empty),
-                Ok(Value::List(vec![Value::String("Hiya".to_string())]))
-            ]
         );
     }
 
     #[test]
     fn evaluate_tool_call() {
-        assert_eq!(evaluate("(output 'Hiya')"), vec![Ok(Value::Empty)]);
+        assert_eq!(evaluate("(output 'Hiya')"), Ok(Value::Empty));
     }
 }

src/main.rs

@@ -32,21 +32,19 @@ fn main() {
         return run_cli_shell();
     }
 
-    let eval_results = if let Some(path) = args.path {
+    let eval_result = if let Some(path) = args.path {
         let file_contents = read_to_string(path).unwrap();
 
         evaluate(&file_contents)
     } else if let Some(command) = args.command {
         evaluate(&command)
     } else {
-        vec![Ok(Value::Empty)]
+        Ok(Value::Empty)
     };
 
-    for result in eval_results {
+    match eval_result {
-        match result {
+        Ok(value) => println!("{value}"),
-            Ok(value) => println!("{value}"),
+        Err(error) => eprintln!("{error}"),
-            Err(error) => eprintln!("{error}"),
-        }
     }
 }
 
@@ -143,21 +141,15 @@ fn run_cli_shell() {
 
                 rl.add_history_entry(line).unwrap();
 
-                let eval_results = evaluate_with_context(line, &mut context);
+                let eval_result = evaluate_with_context(line, &mut context);
 
-                for result in eval_results {
+                match eval_result {
-                    match result {
+                    Ok(value) => println!("{value}"),
-                        Ok(value) => println!("{value}"),
+                    Err(error) => eprintln!("{error}"),
-                        Err(error) => eprintln!("{error}"),
-                    }
                 }
             }
-            Err(ReadlineError::Interrupted) => {
+            Err(ReadlineError::Interrupted) => break,
-                break;
+            Err(ReadlineError::Eof) => break,
-            }
-            Err(ReadlineError::Eof) => {
-                break;
-            }
             Err(error) => eprintln!("{error}"),
         }
     }

src/value/function.rs

@@ -7,11 +7,11 @@ use crate::{Identifier, Item};
 #[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
 pub struct Function {
     parameters: Vec<Identifier>,
-    body: Vec<Item>,
+    body: Item,
 }
 
 impl Function {
-    pub fn new(identifiers: Vec<Identifier>, items: Vec<Item>) -> Self {
+    pub fn new(identifiers: Vec<Identifier>, items: Item) -> Self {
         Function {
             parameters: identifiers,
             body: items,
@@ -22,7 +22,7 @@ impl Function {
         &self.parameters
     }
 
-    pub fn items(&self) -> &Vec<Item> {
+    pub fn body(&self) -> &Item {
         &self.body
     }
 }

src/value/iter.rs

@@ -1,21 +0,0 @@
-use crate::Value;
-
-pub struct Iter(Value);
-
-impl IntoIterator for Value {
-    type Item = Value;
-
-    type IntoIter = Iter;
-
-    fn into_iter(self) -> Self::IntoIter {
-        Iter(self)
-    }
-}
-
-impl Iterator for Iter {
-    type Item = Value;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        todo!()
-    }
-}

src/value/mod.rs

@@ -17,11 +17,10 @@ use std::{
     convert::TryFrom,
     fmt::{self, Display, Formatter},
     marker::PhantomData,
-    ops::{Add, Sub},
+    ops::{Add, AddAssign, Sub, SubAssign},
 };
 
 pub mod function;
-pub mod iter;
 pub mod table;
 pub mod value_type;
 pub mod variable_map;
@@ -157,13 +156,11 @@ impl Value {
             "function" => {
                 let child_count = child.child_count();
                 let mut identifiers = Vec::new();
-                let mut items = Vec::new();
+                let mut item = None;
 
                 for index in 0..child_count {
                     let child = child.child(index).unwrap();
 
-                    println!("{child:?}");
-
                     if child.kind() == "identifier" {
                         let identifier = Identifier::from_syntax_node(child, source)?;
 
@@ -171,13 +168,11 @@ impl Value {
                     }
 
                     if child.kind() == "item" {
-                        let item = Item::from_syntax_node(child, source)?;
+                        item = Some(Item::from_syntax_node(child, source)?);
-
-                        items.push(item)
                     }
                 }
 
-                Ok(Value::Function(Function::new(identifiers, items)))
+                Ok(Value::Function(Function::new(identifiers, item.unwrap())))
             }
             _ => Err(Error::UnexpectedSyntax {
                 expected: "string, integer, float, boolean, list, table, map, function or empty",
@@ -370,54 +365,67 @@ impl Add for Value {
     type Output = Result<Value>;
 
     fn add(self, other: Self) -> Self::Output {
-        match (self, other) {
+        let non_number = match (self, other) {
-            (Value::String(left), Value::String(right)) => {
+            (Value::Integer(left), Value::Integer(right)) => {
-                let concatenated = left + &right;
+                return Ok(Value::Integer(left + right))
+            }
+            (Value::Float(left), Value::Float(right)) => return Ok(Value::Float(left + right)),
+            (Value::Integer(left), Value::Float(right)) => {
+                return Ok(Value::Float(left as f64 + right))
+            }
+            (Value::Float(left), Value::Integer(right)) => {
+                return Ok(Value::Float(left + right as f64))
+            }
+            (non_number, Value::Integer(_)) | (non_number, Value::Float(_)) => non_number,
+            (non_number, _) => non_number,
+        };
 
-                Ok(Value::String(concatenated))
+        Err(Error::ExpectedNumber { actual: non_number })
-            }
-            (Value::String(_), other) | (other, Value::String(_)) => {
-                Err(Error::ExpectedString { actual: other })
-            }
-            (Value::Float(left), Value::Float(right)) => {
-                let addition = left + right;
-
-                Ok(Value::Float(addition))
-            }
-            (Value::Float(_), other) | (other, Value::Float(_)) => {
-                Err(Error::ExpectedFloat { actual: other })
-            }
-            (Value::Integer(left), Value::Integer(right)) => Ok(Value::Integer(left + right)),
-            (Value::Integer(_), other) | (other, Value::Integer(_)) => {
-                Err(Error::ExpectedInt { actual: other })
-            }
-            (Value::Boolean(_), Value::Boolean(_)) => {
-                todo!()
-            }
-            (Value::Boolean(_), other) | (other, Value::Boolean(_)) => {
-                Err(Error::ExpectedBoolean { actual: other })
-            }
-            (Value::List(_), Value::List(_)) => todo!(),
-            (Value::List(_), other) | (other, Value::List(_)) => {
-                Err(Error::ExpectedList { actual: other })
-            }
-            (Value::Map(_), Value::Map(_)) => todo!(),
-            (Value::Map(_), other) | (other, Value::Map(_)) => {
-                Err(Error::ExpectedMap { actual: other })
-            }
-            (Value::Empty, Value::Empty) => Ok(Value::Empty),
-            _ => Err(Error::CustomMessage(
-                "Cannot add the given types.".to_string(),
-            )),
-        }
     }
 }
 
 impl Sub for Value {
     type Output = Result<Self>;
 
-    fn sub(self, _other: Self) -> Self::Output {
+    fn sub(self, other: Self) -> Self::Output {
-        todo!()
+        let non_number = match (self, other) {
+            (Value::Integer(left), Value::Integer(right)) => {
+                return Ok(Value::Integer(left + right))
+            }
+            (Value::Float(left), Value::Float(right)) => return Ok(Value::Float(left + right)),
+            (Value::Integer(left), Value::Float(right)) => {
+                return Ok(Value::Float(left as f64 + right))
+            }
+            (Value::Float(left), Value::Integer(right)) => {
+                return Ok(Value::Float(left + right as f64))
+            }
+            (non_number, Value::Integer(_)) | (non_number, Value::Float(_)) => non_number,
+            (non_number, _) => non_number,
+        };
+
+        Err(Error::ExpectedNumber { actual: non_number })
+    }
+}
+
+impl AddAssign for Value {
+    fn add_assign(&mut self, other: Self) {
+        match (self, other) {
+            (Value::Integer(left), Value::Integer(right)) => *left += right,
+            (Value::Float(left), Value::Float(right)) => *left += right,
+            (Value::Float(left), Value::Integer(right)) => *left += right as f64,
+            _ => {}
+        }
+    }
+}
+
+impl SubAssign for Value {
+    fn sub_assign(&mut self, other: Self) {
+        match (self, other) {
+            (Value::Integer(left), Value::Integer(right)) => *left -= right,
+            (Value::Float(left), Value::Float(right)) => *left -= right,
+            (Value::Float(left), Value::Integer(right)) => *left -= right as f64,
+            _ => {}
+        }
     }
 }
 

tests/dust_examples.rs

@@ -6,52 +6,40 @@ use dust::*;
 fn collections() {
     let file_contents = read_to_string("examples/collections.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }
 
 #[test]
 fn list() {
     let file_contents = read_to_string("examples/list.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }
 
 #[test]
 fn table() {
     let file_contents = read_to_string("examples/table.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }
 
 #[test]
 fn variables() {
     let file_contents = read_to_string("examples/variables.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }
 
 #[test]
 fn scope() {
     let file_contents = read_to_string("examples/scope.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }
 
 #[test]
 fn data_formats() {
     let file_contents = read_to_string("examples/data_formats.ds").unwrap();
 
-    for result in evaluate(&file_contents) {
+    evaluate(&file_contents).unwrap();
-        result.unwrap();
-    }
 }

tree-sitter-dust

@@ -1 +1 @@
-Subproject commit d7ff4e57c58d9ff0708dc2902262384b99c4bc2c
+Subproject commit 532c751c36a1f8c33197b018dd6e947b73abbdc4