Begin implementing control flow with if/else expressions

dust-lang/src/instruction.rs

@@ -150,6 +150,16 @@ impl Instruction {
         instruction
     }
 
+    pub fn equal(comparison_boolean: bool, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Equal as u32);
+
+        instruction.set_destination(if comparison_boolean { 1 } else { 0 });
+        instruction.set_first_argument(left_index);
+        instruction.set_second_argument(right_index);
+
+        instruction
+    }
+
     pub fn negate(to_register: u8, from_index: u8) -> Instruction {
         let mut instruction = Instruction(Operation::Negate as u32);
 
@@ -168,34 +178,35 @@ impl Instruction {
         instruction
     }
 
+    pub fn jump(offset: u8, is_positive: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::Jump as u32);
+
+        instruction.set_first_argument(offset);
+        instruction.set_second_argument(if is_positive { 1 } else { 0 });
+
+        instruction
+    }
+
     pub fn r#return() -> Instruction {
         Instruction(Operation::Return as u32)
     }
 
-    pub fn set_first_argument_to_constant(&mut self) -> &mut Self {
-        self.0 |= 0b1000_0000;
-
-        self
+    pub fn operation(&self) -> Operation {
+        Operation::from((self.0 & 0b0000_0000_0011_1111) as u8)
     }
 
-    pub fn first_argument_is_constant(&self) -> bool {
-        self.0 & 0b1000_0000 != 0
-    }
-
-    pub fn set_second_argument_to_constant(&mut self) -> &mut Self {
-        self.0 |= 0b0100_0000;
-
-        self
-    }
-
-    pub fn second_argument_is_constant(&self) -> bool {
-        self.0 & 0b0100_0000 != 0
+    pub fn set_operation(&mut self, operation: Operation) {
+        self.0 |= u8::from(operation) as u32;
     }
 
     pub fn destination(&self) -> u8 {
         (self.0 >> 24) as u8
     }
 
+    pub fn destination_as_boolean(&self) -> bool {
+        (self.0 >> 24) != 0
+    }
+
     pub fn set_destination(&mut self, destination: u8) {
         self.0 &= 0x00FFFFFF;
         self.0 |= (destination as u32) << 24;
@@ -205,6 +216,20 @@ impl Instruction {
         (self.0 >> 16) as u8
     }
 
+    pub fn first_argument_is_constant(&self) -> bool {
+        self.0 & 0b1000_0000 != 0
+    }
+
+    pub fn first_argument_as_boolean(&self) -> bool {
+        self.first_argument() != 0
+    }
+
+    pub fn set_first_argument_to_constant(&mut self) -> &mut Self {
+        self.0 |= 0b1000_0000;
+
+        self
+    }
+
     pub fn set_first_argument(&mut self, argument: u8) {
         self.0 |= (argument as u32) << 16;
     }
@@ -213,18 +238,24 @@ impl Instruction {
         (self.0 >> 8) as u8
     }
 
+    pub fn second_argument_is_constant(&self) -> bool {
+        self.0 & 0b0100_0000 != 0
+    }
+
+    pub fn second_argument_as_boolean(&self) -> bool {
+        self.second_argument() != 0
+    }
+
+    pub fn set_second_argument_to_constant(&mut self) -> &mut Self {
+        self.0 |= 0b0100_0000;
+
+        self
+    }
+
     pub fn set_second_argument(&mut self, argument: u8) {
         self.0 |= (argument as u32) << 8;
     }
 
-    pub fn operation(&self) -> Operation {
-        Operation::from((self.0 & 0b0000_0000_0011_1111) as u8)
-    }
-
-    pub fn set_operation(&mut self, operation: Operation) {
-        self.0 |= u8::from(operation) as u32;
-    }
-
     pub fn disassemble(&self, chunk: &Chunk) -> String {
         let mut disassembled = format!("{:16} ", self.operation().to_string());
 
@@ -263,14 +294,14 @@ impl Instruction {
             }
             Operation::LoadBoolean => {
                 let to_register = self.destination();
-                let boolean = if self.first_argument() == 0 {
-                    "false"
+                let boolean = self.first_argument_as_boolean();
+                let skip_display = if self.second_argument_as_boolean() {
+                    "IP++"
                 } else {
-                    "true"
+                    ""
                 };
-                let skip = self.second_argument() != 0;
 
-                format!("R({to_register}) = {boolean}; if {skip} ip++",)
+                format!("R({to_register}) = {boolean} {skip_display}",)
             }
             Operation::LoadConstant => {
                 let constant_index = self.first_argument();
@@ -389,6 +420,37 @@ impl Instruction {
 
                 format!("R({destination}) = {first_argument} || {second_argument}",)
             }
+            Operation::Equal => {
+                let comparison_symbol = if self.destination_as_boolean() {
+                    "=="
+                } else {
+                    "!="
+                };
+
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} IP++",)
+            }
+            Operation::Less => {
+                let comparison_symbol = if self.destination_as_boolean() {
+                    "<"
+                } else {
+                    ">="
+                };
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} IP++",)
+            }
+            Operation::LessEqual => {
+                let comparison_symbol = if self.destination_as_boolean() {
+                    "<="
+                } else {
+                    ">"
+                };
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} IP++",)
+            }
             Operation::Negate => {
                 let destination = self.destination();
                 let argument = if self.first_argument_is_constant() {
@@ -409,6 +471,16 @@ impl Instruction {
 
                 format!("R({destination}) = !{argument}")
             }
+            Operation::Jump => {
+                let offset = self.first_argument();
+                let positive = self.second_argument() != 0;
+
+                if positive {
+                    format!("IP += {}", offset)
+                } else {
+                    format!("IP -= {}", offset)
+                }
+            }
             Operation::Return => return None,
         };
 
@@ -453,6 +525,16 @@ mod tests {
         assert_eq!(instruction.second_argument(), 2);
     }
 
+    #[test]
+    fn load_boolean() {
+        let instruction = Instruction::load_boolean(4, true, true);
+
+        assert_eq!(instruction.operation(), Operation::LoadBoolean);
+        assert_eq!(instruction.destination(), 4);
+        assert!(instruction.first_argument_as_boolean());
+        assert!(instruction.second_argument_as_boolean());
+    }
+
     #[test]
     fn load_constant() {
         let mut instruction = Instruction::load_constant(0, 1);
@@ -484,8 +566,6 @@ mod tests {
     fn add() {
         let mut instruction = Instruction::add(1, 1, 0);
 
-        instruction.set_operation(Operation::Add);
-
         instruction.set_first_argument_to_constant();
 
         assert_eq!(instruction.operation(), Operation::Add);
@@ -499,8 +579,6 @@ mod tests {
     fn subtract() {
         let mut instruction = Instruction::subtract(0, 1, 2);
 
-        instruction.set_operation(Operation::Subtract);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -516,8 +594,6 @@ mod tests {
     fn multiply() {
         let mut instruction = Instruction::multiply(0, 1, 2);
 
-        instruction.set_operation(Operation::Multiply);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -533,8 +609,6 @@ mod tests {
     fn divide() {
         let mut instruction = Instruction::divide(0, 1, 2);
 
-        instruction.set_operation(Operation::Divide);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -550,8 +624,6 @@ mod tests {
     fn and() {
         let mut instruction = Instruction::and(0, 1, 2);
 
-        instruction.set_operation(Operation::And);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -567,8 +639,6 @@ mod tests {
     fn or() {
         let mut instruction = Instruction::or(0, 1, 2);
 
-        instruction.set_operation(Operation::Or);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -580,12 +650,25 @@ mod tests {
         assert!(instruction.second_argument_is_constant());
     }
 
+    #[test]
+    fn equal() {
+        let mut instruction = Instruction::equal(true, 1, 2);
+
+        instruction.set_first_argument_to_constant();
+        instruction.set_second_argument_to_constant();
+
+        assert_eq!(instruction.operation(), Operation::Equal);
+        assert!(instruction.destination_as_boolean());
+        assert_eq!(instruction.first_argument(), 1);
+        assert_eq!(instruction.second_argument(), 2);
+        assert!(instruction.first_argument_is_constant());
+        assert!(instruction.second_argument_is_constant());
+    }
+
     #[test]
     fn negate() {
         let mut instruction = Instruction::negate(0, 1);
 
-        instruction.set_operation(Operation::Negate);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -600,8 +683,6 @@ mod tests {
     fn not() {
         let mut instruction = Instruction::not(0, 1);
 
-        instruction.set_operation(Operation::Not);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 
@@ -612,12 +693,22 @@ mod tests {
         assert!(instruction.second_argument_is_constant());
     }
 
+    #[test]
+    fn jump() {
+        let mut instruction = Instruction::jump(4, true);
+
+        instruction.set_first_argument_to_constant();
+        instruction.set_second_argument_to_constant();
+
+        assert_eq!(instruction.operation(), Operation::Jump);
+        assert_eq!(instruction.first_argument(), 4);
+        assert!(instruction.first_argument_as_boolean());
+    }
+
     #[test]
     fn r#return() {
         let mut instruction = Instruction::r#return();
 
-        instruction.set_operation(Operation::Return);
-
         instruction.set_first_argument_to_constant();
         instruction.set_second_argument_to_constant();
 

dust-lang/src/operation.rs

@@ -2,22 +2,32 @@ use std::fmt::{self, Display, Formatter};
 
 const MOVE: u8 = 0b0000_0000;
 const CLOSE: u8 = 0b000_0001;
+
 const LOAD_BOOLEAN: u8 = 0b0000_0010;
 const LOAD_CONSTANT: u8 = 0b0000_0011;
 const LOAD_LIST: u8 = 0b0000_0100;
+
 const DECLARE_LOCAL: u8 = 0b0000_0101;
 const GET_LOCAL: u8 = 0b0000_0110;
 const SET_LOCAL: u8 = 0b0000_0111;
+
 const ADD: u8 = 0b0000_1000;
 const SUBTRACT: u8 = 0b0000_1001;
 const MULTIPLY: u8 = 0b0000_1010;
-const MODULO: u8 = 0b0000_1011;
-const AND: u8 = 0b0000_1100;
-const OR: u8 = 0b0000_1101;
-const DIVIDE: u8 = 0b0000_1110;
-const NEGATE: u8 = 0b0000_1111;
-const NOT: u8 = 0b0001_0000;
-const RETURN: u8 = 0b0001_0001;
+const DIVIDE: u8 = 0b0000_1011;
+const MODULO: u8 = 0b0000_1100;
+const AND: u8 = 0b0000_1101;
+const OR: u8 = 0b0000_1110;
+
+const EQUAL: u8 = 0b0000_1111;
+const LESS: u8 = 0b0001_0000;
+const LESS_EQUAL: u8 = 0b0001_0001;
+
+const NEGATE: u8 = 0b0001_0010;
+const NOT: u8 = 0b0001_0011;
+
+const JUMP: u8 = 0b0001_0100;
+const RETURN: u8 = 0b0001_0101;
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Operation {
@@ -44,11 +54,17 @@ pub enum Operation {
     And = AND as isize,
     Or = OR as isize,
 
+    // Relational operations
+    Equal = EQUAL as isize,
+    Less = LESS as isize,
+    LessEqual = LESS_EQUAL as isize,
+
     // Unary operations
     Negate = NEGATE as isize,
     Not = NOT as isize,
 
     // Control flow
+    Jump = JUMP as isize,
     Return = RETURN as isize,
 }
 
@@ -85,8 +101,12 @@ impl From<u8> for Operation {
             MODULO => Operation::Modulo,
             AND => Operation::And,
             OR => Operation::Or,
+            EQUAL => Operation::Equal,
+            LESS => Operation::Less,
+            LESS_EQUAL => Operation::LessEqual,
             NEGATE => Operation::Negate,
             NOT => Operation::Not,
+            JUMP => Operation::Jump,
             RETURN => Operation::Return,
             _ => {
                 if cfg!(test) {
@@ -117,8 +137,12 @@ impl From<Operation> for u8 {
             Operation::Modulo => MODULO,
             Operation::And => AND,
             Operation::Or => OR,
+            Operation::Equal => EQUAL,
+            Operation::Less => LESS,
+            Operation::LessEqual => LESS_EQUAL,
             Operation::Negate => NEGATE,
             Operation::Not => NOT,
+            Operation::Jump => JUMP,
             Operation::Return => RETURN,
         }
     }
@@ -142,8 +166,12 @@ impl Display for Operation {
             Operation::Modulo => write!(f, "MODULO"),
             Operation::And => write!(f, "AND"),
             Operation::Or => write!(f, "OR"),
+            Operation::Equal => write!(f, "EQUAL"),
+            Operation::Less => write!(f, "LESS"),
+            Operation::LessEqual => write!(f, "LESS_EQUAL"),
             Operation::Negate => write!(f, "NEGATE"),
             Operation::Not => write!(f, "NOT"),
+            Operation::Jump => write!(f, "JUMP"),
             Operation::Return => write!(f, "RETURN"),
         }
     }

dust-lang/src/parser/mod.rs

@@ -153,6 +153,7 @@ impl<'src> Parser<'src> {
                 Instruction::load_boolean(self.current_register, boolean, false),
                 self.previous_position,
             );
+            self.increment_register()?;
         }
 
         Ok(())
@@ -382,6 +383,7 @@ impl<'src> Parser<'src> {
             TokenKind::Percent => Instruction::modulo(self.current_register, left, right),
             TokenKind::DoubleAmpersand => Instruction::and(self.current_register, left, right),
             TokenKind::DoublePipe => Instruction::or(self.current_register, left, right),
+            TokenKind::DoubleEqual => Instruction::equal(true, left, right),
             _ => {
                 return Err(ParseError::ExpectedTokenMultiple {
                     expected: &[
@@ -392,6 +394,7 @@ impl<'src> Parser<'src> {
                         TokenKind::Percent,
                         TokenKind::DoubleAmpersand,
                         TokenKind::DoublePipe,
+                        TokenKind::DoubleEqual,
                     ],
                     found: operator.to_owned(),
                     position: operator_position,
@@ -418,6 +421,10 @@ impl<'src> Parser<'src> {
         self.emit_instruction(instruction, operator_position);
         self.increment_register()?;
 
+        if let TokenKind::DoubleEqual = operator.kind() {
+            self.emit_instruction(Instruction::jump(2, true), operator_position);
+        }
+
         Ok(())
     }
 
@@ -521,14 +528,17 @@ impl<'src> Parser<'src> {
             ends_with_semicolon = true;
         }
 
+        let end = self.current_position.1;
+
         if ends_with_semicolon {
-            let end = self.current_position.1;
             let end_register = self.current_register;
 
             self.emit_instruction(
                 Instruction::close(start_register, end_register),
                 Span(start, end),
             );
+        } else {
+            self.emit_instruction(Instruction::r#return(), Span(start, end));
         }
 
         Ok(())
@@ -572,6 +582,18 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
+    fn parse_if(&mut self, _allow_assignment: bool) -> Result<(), ParseError> {
+        self.advance()?;
+        self.parse_expression()?;
+        self.parse_block(false)?;
+
+        if self.allow(TokenKind::Else)? {
+            self.parse_block(false)?;
+        }
+
+        Ok(())
+    }
+
     fn parse_expression(&mut self) -> Result<(), ParseError> {
         self.parse(Precedence::None)
     }
@@ -784,9 +806,17 @@ impl From<&TokenKind> for ParseRule<'_> {
             TokenKind::Async => todo!(),
             TokenKind::Bool => todo!(),
             TokenKind::Break => todo!(),
-            TokenKind::Else => todo!(),
+            TokenKind::Else => ParseRule {
+                prefix: None,
+                infix: None,
+                precedence: Precedence::None,
+            },
             TokenKind::FloatKeyword => todo!(),
-            TokenKind::If => todo!(),
+            TokenKind::If => ParseRule {
+                prefix: Some(Parser::parse_if),
+                infix: None,
+                precedence: Precedence::None,
+            },
             TokenKind::Int => todo!(),
             TokenKind::Let => ParseRule {
                 prefix: Some(Parser::parse_let_statement),
@@ -816,7 +846,11 @@ impl From<&TokenKind> for ParseRule<'_> {
                 precedence: Precedence::LogicalAnd,
             },
             TokenKind::DoubleDot => todo!(),
-            TokenKind::DoubleEqual => todo!(),
+            TokenKind::DoubleEqual => ParseRule {
+                prefix: None,
+                infix: Some(Parser::parse_binary),
+                precedence: Precedence::Equality,
+            },
             TokenKind::DoublePipe => ParseRule {
                 prefix: None,
                 infix: Some(Parser::parse_binary),

dust-lang/src/vm.rs

@@ -77,13 +77,13 @@ impl Vm {
                 }
                 Operation::LoadBoolean => {
                     let to_register = instruction.destination();
-                    let boolean = instruction.first_argument() != 0;
-                    let skip = instruction.second_argument() != 0;
+                    let boolean = instruction.first_argument_as_boolean();
+                    let skip = instruction.second_argument_as_boolean();
                     let value = Value::boolean(boolean);
 
                     self.insert(value, to_register, position)?;
 
-                    if skip {
+                    if boolean && skip {
                         self.ip += 1;
                     }
                 }
@@ -201,6 +201,45 @@ impl Vm {
 
                     self.insert(or, instruction.destination(), position)?;
                 }
+                Operation::Equal => {
+                    let (left, right) = take_constants_or_clone(self, instruction, position)?;
+                    let equal = left
+                        .equal(&right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let compare_to = instruction.destination_as_boolean();
+
+                    if let Some(boolean) = equal.as_boolean() {
+                        if boolean == compare_to {
+                            self.ip += 1;
+                        }
+                    }
+                }
+                Operation::Less => {
+                    let (left, right) = take_constants_or_clone(self, instruction, position)?;
+                    let less = left
+                        .less_than(&right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let compare_to = instruction.destination() != 0;
+
+                    if let Some(boolean) = less.as_boolean() {
+                        if boolean != compare_to {
+                            self.ip += 1;
+                        }
+                    }
+                }
+                Operation::LessEqual => {
+                    let (left, right) = take_constants_or_clone(self, instruction, position)?;
+                    let less_equal = left
+                        .less_than_or_equal(&right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let compare_to = instruction.destination() != 0;
+
+                    if let Some(boolean) = less_equal.as_boolean() {
+                        if boolean != compare_to {
+                            self.ip += 1;
+                        }
+                    }
+                }
                 Operation::Negate => {
                     let value = if instruction.first_argument_is_constant() {
                         self.chunk
@@ -227,6 +266,17 @@ impl Vm {
 
                     self.insert(not, instruction.destination(), position)?;
                 }
+                Operation::Jump => {
+                    let offset = instruction.first_argument();
+                    let is_positive = instruction.second_argument_as_boolean();
+                    let new_ip = if is_positive {
+                        self.ip + offset as usize
+                    } else {
+                        self.ip - offset as usize
+                    };
+
+                    self.ip = new_ip;
+                }
                 Operation::Return => {
                     let value = self.pop(position)?;