Add while loops

dust-lang/src/abstract_tree.rs

@@ -57,8 +57,15 @@ pub enum Statement {
     },
 
     // Property access expression
+    // TODO: This should be a binary operation
     PropertyAccess(Box<Node<Statement>>, Box<Node<Statement>>),
 
+    // Loops
+    While {
+        condition: Box<Node<Statement>>,
+        body: Box<Node<Statement>>,
+    },
+
     // Identifier expression
     Identifier(Identifier),
 
@@ -78,7 +85,27 @@ impl Statement {
     pub fn expected_type(&self, context: &Context) -> Option<Type> {
         match self {
             Statement::Block(nodes) => nodes.last().unwrap().inner.expected_type(context),
-            Statement::BinaryOperation { left, .. } => left.inner.expected_type(context),
+            Statement::BinaryOperation {
+                left,
+                operator,
+                right,
+            } => match operator.inner {
+                BinaryOperator::Add
+                | BinaryOperator::Divide
+                | BinaryOperator::Modulo
+                | BinaryOperator::Multiply
+                | BinaryOperator::Subtract => Some(left.inner.expected_type(context)?),
+
+                BinaryOperator::Equal
+                | BinaryOperator::Greater
+                | BinaryOperator::GreaterOrEqual
+                | BinaryOperator::Less
+                | BinaryOperator::LessOrEqual
+                | BinaryOperator::And
+                | BinaryOperator::Or => Some(Type::Boolean),
+
+                BinaryOperator::Assign | BinaryOperator::AddAssign => None,
+            },
             Statement::BuiltInFunctionCall { function, .. } => function.expected_return_type(),
             Statement::Constant(value) => Some(value.r#type(context)),
             Statement::FunctionCall { function, .. } => function.inner.expected_type(context),
@@ -102,8 +129,9 @@ impl Statement {
 
                 Some(Type::Map(types))
             }
-            Statement::PropertyAccess(_, _) => None,
             Statement::Nil(_) => None,
+            Statement::PropertyAccess(_, _) => None,
+            Statement::While { .. } => None,
         }
     }
 }
@@ -231,6 +259,9 @@ impl Display for Statement {
             }
             Statement::Nil(node) => write!(f, "{node};"),
             Statement::PropertyAccess(left, right) => write!(f, "{left}.{right}"),
+            Statement::While { condition, body } => {
+                write!(f, "while {condition} {body}")
+            }
         }
     }
 }

dust-lang/src/analyzer.rs

@@ -178,6 +178,9 @@ impl<'a> Analyzer<'a> {
                     self.analyze_node(value_node)?;
                 }
             }
+            Statement::Nil(node) => {
+                self.analyze_node(node)?;
+            }
             Statement::PropertyAccess(left, right) => {
                 if let Statement::Identifier(_) | Statement::Constant(_) | Statement::List(_) =
                     &left.inner
@@ -204,8 +207,17 @@ impl<'a> Analyzer<'a> {
 
                 self.analyze_node(right)?;
             }
-            Statement::Nil(node) => {
+            Statement::While { condition, body } => {
-                self.analyze_node(node)?;
+                self.analyze_node(condition)?;
+                self.analyze_node(body)?;
+
+                if let Some(Type::Boolean) = condition.inner.expected_type(self.context) {
+                } else {
+                    return Err(AnalyzerError::ExpectedBoolean {
+                        actual: condition.as_ref().clone(),
+                        position: condition.position,
+                    });
+                }
             }
         }
 

dust-lang/src/lex.rs

@@ -403,6 +403,7 @@ impl Lexer {
             "length" => Token::Length,
             "NaN" => Token::Float("NaN"),
             "read_line" => Token::ReadLine,
+            "while" => Token::While,
             "write_line" => Token::WriteLine,
             _ => Token::Identifier(string),
         };
@@ -475,6 +476,27 @@ impl Display for LexError {
 mod tests {
     use super::*;
 
+    #[test]
+    fn while_loop() {
+        let input = "while x < 10 { x += 1 }";
+
+        assert_eq!(
+            lex(input),
+            Ok(vec![
+                (Token::While, (0, 5)),
+                (Token::Identifier("x"), (6, 7)),
+                (Token::Less, (8, 9)),
+                (Token::Integer("10"), (10, 12)),
+                (Token::LeftCurlyBrace, (13, 14)),
+                (Token::Identifier("x"), (15, 16)),
+                (Token::PlusEqual, (17, 19)),
+                (Token::Integer("1"), (20, 21)),
+                (Token::RightCurlyBrace, (22, 23)),
+                (Token::Eof, (23, 23)),
+            ])
+        )
+    }
+
     #[test]
     fn add_assign() {
         let input = "x += 42";

dust-lang/src/parse.rs

@@ -416,6 +416,31 @@ impl<'src> Parser<'src> {
                     left_position,
                 ))
             }
+            (Token::While, left_position) => {
+                self.next_token()?;
+
+                let condition = self.parse_statement(0)?;
+
+                if let Token::LeftCurlyBrace = self.current.0 {
+                } else {
+                    return Err(ParseError::ExpectedToken {
+                        expected: TokenOwned::LeftCurlyBrace,
+                        actual: self.current.0.to_owned(),
+                        position: self.current.1,
+                    });
+                }
+
+                let body = self.parse_block()?;
+                let body_end = body.position.1;
+
+                Ok(Node::new(
+                    Statement::While {
+                        condition: Box::new(condition),
+                        body: Box::new(body),
+                    },
+                    (left_position.0, body_end),
+                ))
+            }
             _ => Err(ParseError::UnexpectedToken {
                 actual: self.current.0.to_owned(),
                 position: self.current.1,
@@ -498,6 +523,39 @@ impl<'src> Parser<'src> {
             Ok(left)
         }
     }
+
+    fn parse_block(&mut self) -> Result<Node<Statement>, ParseError> {
+        let left_start = self.current.1 .0;
+
+        if let Token::LeftCurlyBrace = self.current.0 {
+            self.next_token()?;
+        } else {
+            return Err(ParseError::ExpectedToken {
+                expected: TokenOwned::LeftCurlyBrace,
+                actual: self.current.0.to_owned(),
+                position: self.current.1,
+            });
+        }
+
+        let mut statements = Vec::new();
+
+        loop {
+            if let Token::RightCurlyBrace = self.current.0 {
+                let right_end = self.current.1 .1;
+
+                self.next_token()?;
+
+                return Ok(Node::new(
+                    Statement::Block(statements),
+                    (left_start, right_end),
+                ));
+            }
+
+            let statement = self.parse_statement(0)?;
+
+            statements.push(statement);
+        }
+    }
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -583,6 +641,54 @@ mod tests {
 
     use super::*;
 
+    #[test]
+    fn while_loop() {
+        let input = "while x < 10 { x += 1 }";
+
+        assert_eq!(
+            parse(input),
+            Ok(AbstractSyntaxTree {
+                nodes: [Node::new(
+                    Statement::While {
+                        condition: Box::new(Node::new(
+                            Statement::BinaryOperation {
+                                left: Box::new(Node::new(
+                                    Statement::Identifier(Identifier::new("x")),
+                                    (6, 7)
+                                )),
+                                operator: Node::new(BinaryOperator::Less, (8, 9)),
+                                right: Box::new(Node::new(
+                                    Statement::Constant(Value::integer(10)),
+                                    (10, 12)
+                                )),
+                            },
+                            (6, 12)
+                        )),
+                        body: Box::new(Node::new(
+                            Statement::Block(vec![Node::new(
+                                Statement::BinaryOperation {
+                                    left: Box::new(Node::new(
+                                        Statement::Identifier(Identifier::new("x")),
+                                        (15, 16)
+                                    )),
+                                    operator: Node::new(BinaryOperator::AddAssign, (17, 19)),
+                                    right: Box::new(Node::new(
+                                        Statement::Constant(Value::integer(1)),
+                                        (20, 21)
+                                    )),
+                                },
+                                (15, 21)
+                            )]),
+                            (13, 23)
+                        )),
+                    },
+                    (0, 23)
+                )]
+                .into()
+            })
+        );
+    }
+
     #[test]
     fn add_assign() {
         let input = "a += 1";

dust-lang/src/token.rs

@@ -21,6 +21,7 @@ pub enum Token<'src> {
     IsOdd,
     Length,
     ReadLine,
+    While,
     WriteLine,
 
     // Symbols
@@ -85,6 +86,7 @@ impl<'src> Token<'src> {
             Token::Star => TokenOwned::Star,
             Token::Slash => TokenOwned::Slash,
             Token::String(text) => TokenOwned::String(text.to_string()),
+            Token::While => TokenOwned::While,
             Token::WriteLine => TokenOwned::WriteLine,
         }
     }
@@ -124,6 +126,7 @@ impl<'src> Token<'src> {
             Token::Star => "*",
             Token::String(_) => "string",
             Token::Slash => "/",
+            Token::While => "while",
             Token::WriteLine => "write_line",
         }
     }
@@ -205,6 +208,7 @@ impl<'src> PartialEq for Token<'src> {
             (Token::Star, Token::Star) => true,
             (Token::Slash, Token::Slash) => true,
             (Token::String(left), Token::String(right)) => left == right,
+            (Token::While, Token::While) => true,
             (Token::WriteLine, Token::WriteLine) => true,
             _ => false,
         }
@@ -231,6 +235,7 @@ pub enum TokenOwned {
     IsOdd,
     Length,
     ReadLine,
+    While,
     WriteLine,
 
     // Symbols
@@ -295,6 +300,7 @@ impl Display for TokenOwned {
             TokenOwned::Star => Token::Star.fmt(f),
             TokenOwned::Slash => Token::Slash.fmt(f),
             TokenOwned::String(string) => write!(f, "{string}"),
+            TokenOwned::While => Token::While.fmt(f),
             TokenOwned::WriteLine => Token::WriteLine.fmt(f),
         }
     }

dust-lang/src/vm.rs

@@ -6,8 +6,9 @@ use std::{
 };
 
 use crate::{
-    abstract_tree::BinaryOperator, parse, AbstractSyntaxTree, Analyzer, AnalyzerError,
+    abstract_tree::BinaryOperator, parse, value::ValueInner, AbstractSyntaxTree, Analyzer,
-    BuiltInFunctionError, Context, Node, ParseError, Span, Statement, Value, ValueError,
+    AnalyzerError, BuiltInFunctionError, Context, Node, ParseError, Span, Statement, Value,
+    ValueError,
 };
 
 pub fn run(input: &str, context: &mut Context) -> Result<Option<Value>, VmError> {
@@ -348,6 +349,31 @@ impl Vm {
                     position: right_span,
                 })
             }
+            Statement::While { condition, body } => {
+                let mut return_value = None;
+
+                let condition_position = condition.position;
+
+                while let Some(condition_value) = self.run_node(*condition.clone(), context)? {
+                    if let ValueInner::Boolean(condition_value) = condition_value.inner().as_ref() {
+                        if !condition_value {
+                            break;
+                        }
+                    } else {
+                        return Err(VmError::ExpectedBoolean {
+                            position: condition_position,
+                        });
+                    }
+
+                    return_value = self.run_node(*body.clone(), context)?;
+
+                    if return_value.is_some() {
+                        break;
+                    }
+                }
+
+                Ok(return_value)
+            }
         }
     }
 }
@@ -367,6 +393,9 @@ pub enum VmError {
         error: BuiltInFunctionError,
         position: Span,
     },
+    ExpectedBoolean {
+        position: Span,
+    },
     ExpectedIdentifier {
         position: Span,
     },
@@ -398,6 +427,7 @@ impl VmError {
             Self::ParseError(parse_error) => parse_error.position(),
             Self::ValueError { position, .. } => *position,
             Self::BuiltInFunctionError { position, .. } => *position,
+            Self::ExpectedBoolean { position } => *position,
             Self::ExpectedIdentifier { position } => *position,
             Self::ExpectedIdentifierOrInteger { position } => *position,
             Self::ExpectedInteger { position } => *position,
@@ -442,6 +472,9 @@ impl Display for VmError {
             Self::BuiltInFunctionError { error, .. } => {
                 write!(f, "{}", error)
             }
+            Self::ExpectedBoolean { position } => {
+                write!(f, "Expected a boolean at position: {:?}", position)
+            }
             Self::ExpectedFunction { actual, position } => {
                 write!(
                     f,
@@ -479,6 +512,13 @@ impl Display for VmError {
 mod tests {
     use super::*;
 
+    #[test]
+    fn while_loop() {
+        let input = "x = 0; while x < 5 { x += 1; } x";
+
+        assert_eq!(run(input, &mut Context::new()), Ok(Some(Value::integer(5))));
+    }
+
     #[test]
     fn add_assign() {
         let input = "x = 1; x += 1; x";