comments, if then else

.gitignore

@@ -25,3 +25,4 @@ go.work.sum
 # env file
 .env
 
+/test.mako

compiler/compiler.go

@@ -110,6 +110,10 @@ func (c *compiler) compileExpression(expr parser.Expression) {
 		constIndex := c.addConstant(e.Value)
 		c.emit(types.OpConstant, constIndex)
 
+	case *parser.BooleanLiteral:
+		constIndex := c.addConstant(e.Value)
+		c.emit(types.OpConstant, constIndex)
+
 	case *parser.Identifier:
 		nameIndex := c.addConstant(e.Value)
 
@@ -147,7 +151,7 @@ func (c *compiler) compileExpression(expr parser.Expression) {
 		c.compileExpression(e.Index)
 		c.emit(types.OpGetIndex, 0)
 
-	// New expression types for arithmetic
+	// Arithmetic expressions
 	case *parser.InfixExpression:
 		// Compile left and right expressions
 		c.compileExpression(e.Left)
@@ -163,6 +167,18 @@ func (c *compiler) compileExpression(expr parser.Expression) {
 			c.emit(types.OpMultiply, 0)
 		case "/":
 			c.emit(types.OpDivide, 0)
+		case "==":
+			c.emit(types.OpEqual, 0)
+		case "!=":
+			c.emit(types.OpNotEqual, 0)
+		case "<":
+			c.emit(types.OpLessThan, 0)
+		case ">":
+			c.emit(types.OpGreaterThan, 0)
+		case "<=":
+			c.emit(types.OpLessEqual, 0)
+		case ">=":
+			c.emit(types.OpGreaterEqual, 0)
 		default:
 			panic(fmt.Sprintf("Unknown infix operator: %s", e.Operator))
 		}
@@ -182,6 +198,80 @@ func (c *compiler) compileExpression(expr parser.Expression) {
 	case *parser.GroupedExpression:
 		// Just compile the inner expression
 		c.compileExpression(e.Expr)
+
+	case *parser.IfExpression:
+		// Compile condition
+		c.compileExpression(e.Condition)
+
+		// Emit jump-if-false with placeholder
+		jumpNotTruePos := len(c.instructions)
+		c.emit(types.OpJumpIfFalse, 0) // Will backpatch
+
+		// Compile consequence (then block)
+		lastStmtIndex := len(e.Consequence.Statements) - 1
+		for i, stmt := range e.Consequence.Statements {
+			if i == lastStmtIndex {
+				// For the last statement, we need to ensure it leaves a value
+				if exprStmt, ok := stmt.(*parser.ExpressionStatement); ok {
+					c.compileExpression(exprStmt.Expression)
+				} else {
+					c.compileStatement(stmt)
+					// Push null if not an expression statement
+					nullIndex := c.addConstant(nil)
+					c.emit(types.OpConstant, nullIndex)
+				}
+			} else {
+				c.compileStatement(stmt)
+			}
+		}
+
+		// If no statements, push null
+		if len(e.Consequence.Statements) == 0 {
+			nullIndex := c.addConstant(nil)
+			c.emit(types.OpConstant, nullIndex)
+		}
+
+		// Emit jump to skip else part
+		jumpPos := len(c.instructions)
+		c.emit(types.OpJump, 0) // Will backpatch
+
+		// Backpatch jump-if-false to point to else
+		afterConsequencePos := len(c.instructions)
+		c.instructions[jumpNotTruePos].Operand = afterConsequencePos
+
+		// Compile alternative (else block)
+		if e.Alternative != nil {
+			lastStmtIndex = len(e.Alternative.Statements) - 1
+			for i, stmt := range e.Alternative.Statements {
+				if i == lastStmtIndex {
+					// For the last statement, we need to ensure it leaves a value
+					if exprStmt, ok := stmt.(*parser.ExpressionStatement); ok {
+						c.compileExpression(exprStmt.Expression)
+					} else {
+						c.compileStatement(stmt)
+						// Push null if not an expression statement
+						nullIndex := c.addConstant(nil)
+						c.emit(types.OpConstant, nullIndex)
+					}
+				} else {
+					c.compileStatement(stmt)
+				}
+			}
+
+			// If no statements, push null
+			if len(e.Alternative.Statements) == 0 {
+				nullIndex := c.addConstant(nil)
+				c.emit(types.OpConstant, nullIndex)
+			}
+		} else {
+			// No else - push null
+			nullIndex := c.addConstant(nil)
+			c.emit(types.OpConstant, nullIndex)
+		}
+
+		// Backpatch jump to point after else
+		afterAlternativePos := len(c.instructions)
+		c.instructions[jumpPos].Operand = afterAlternativePos
 	}
 }
 

lexer/lexer.go

@@ -21,6 +21,18 @@ const (
 	TokenSlash
 	TokenLeftParen
 	TokenRightParen
+	TokenIf
+	TokenThen
+	TokenElse
+	TokenTrue
+	TokenFalse
+	TokenEqualEqual
+	TokenNotEqual
+	TokenLessThan
+	TokenGreaterThan
+	TokenLessEqual
+	TokenGreaterEqual
+	TokenEnd
 )
 
 type Token struct {
@@ -55,10 +67,37 @@ func (l *Lexer) NextToken() Token {
 	var tok Token
 
 	l.skipWhitespace()
+	l.skipComment()
 
 	switch l.ch {
 	case '=':
-		tok = Token{Type: TokenEqual, Value: "="}
+		if l.peekChar() == '=' {
+			l.readChar() // consume the current '='
+			tok = Token{Type: TokenEqualEqual, Value: "=="}
+		} else {
+			tok = Token{Type: TokenEqual, Value: "="}
+		}
+	case '!':
+		if l.peekChar() == '=' {
+			l.readChar() // consume the current '!'
+			tok = Token{Type: TokenNotEqual, Value: "!="}
+		} else {
+			tok = Token{Type: TokenEOF, Value: ""} // Not supported yet
+		}
+	case '<':
+		if l.peekChar() == '=' {
+			l.readChar() // consume the current '<'
+			tok = Token{Type: TokenLessEqual, Value: "<="}
+		} else {
+			tok = Token{Type: TokenLessThan, Value: "<"}
+		}
+	case '>':
+		if l.peekChar() == '=' {
+			l.readChar() // consume the current '>'
+			tok = Token{Type: TokenGreaterEqual, Value: ">="}
+		} else {
+			tok = Token{Type: TokenGreaterThan, Value: ">"}
+		}
 	case ';':
 		tok = Token{Type: TokenSemicolon, Value: ";"}
 	case '"':
@@ -74,7 +113,6 @@ func (l *Lexer) NextToken() Token {
 		tok = Token{Type: TokenRightBracket, Value: "]"}
 	case ',':
 		tok = Token{Type: TokenComma, Value: ","}
-	// New arithmetic operators
 	case '+':
 		tok = Token{Type: TokenPlus, Value: "+"}
 	case '-':
@@ -92,9 +130,22 @@ func (l *Lexer) NextToken() Token {
 	default:
 		if isLetter(l.ch) {
 			tok.Value = l.readIdentifier()
-			if tok.Value == "echo" {
+			switch tok.Value {
+			case "echo":
 				tok.Type = TokenEcho
-			} else {
+			case "if":
+				tok.Type = TokenIf
+			case "then":
+				tok.Type = TokenThen
+			case "else":
+				tok.Type = TokenElse
+			case "true":
+				tok.Type = TokenTrue
+			case "false":
+				tok.Type = TokenFalse
+			case "end":
+				tok.Type = TokenEnd
+			default:
 				tok.Type = TokenIdentifier
 			}
 			return tok
@@ -153,3 +204,23 @@ func isLetter(ch byte) bool {
 func isDigit(ch byte) bool {
 	return '0' <= ch && ch <= '9'
 }
+
+func (l *Lexer) peekChar() byte {
+	if l.readPos >= len(l.input) {
+		return 0
+	}
+	return l.input[l.readPos]
+}
+
+func (l *Lexer) skipComment() {
+	if l.ch == '/' && l.peekChar() == '/' {
+		l.readChar()
+		l.readChar()
+
+		for l.ch != '\n' && l.ch != 0 {
+			l.readChar()
+		}
+
+		l.skipWhitespace()
+	}
+}

mako.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+
+	"git.sharkk.net/Sharkk/Mako/compiler"
+	"git.sharkk.net/Sharkk/Mako/lexer"
+	"git.sharkk.net/Sharkk/Mako/parser"
+	"git.sharkk.net/Sharkk/Mako/vm"
+)
+
+func RunRepl() {
+	scanner := bufio.NewScanner(os.Stdin)
+	virtualMachine := vm.New()
+
+	fmt.Println("Mako REPL (type 'exit' to quit)")
+	for {
+		fmt.Print(">> ")
+		if !scanner.Scan() {
+			break
+		}
+
+		input := scanner.Text()
+		if input == "exit" {
+			break
+		}
+
+		ExecuteCode(input, virtualMachine)
+	}
+}
+
+func ExecuteCode(code string, virtualMachine *vm.VM) {
+	lex := lexer.New(code)
+	p := parser.New(lex)
+	program := p.ParseProgram()
+
+	if len(p.Errors()) > 0 {
+		for _, err := range p.Errors() {
+			fmt.Printf("Error: %s\n", err)
+		}
+		return
+	}
+
+	bytecode := compiler.Compile(program)
+	virtualMachine.Run(bytecode)
+}
+
+func main() {
+	args := os.Args[1:]
+
+	// If there's a command line argument, try to execute it as a file
+	if len(args) > 0 {
+		filename := args[0]
+		fileContent, err := os.ReadFile(filename)
+		if err != nil {
+			fmt.Printf("Error reading file %s: %v\n", filename, err)
+			os.Exit(1)
+		}
+
+		// Execute the file content
+		ExecuteCode(string(fileContent), vm.New())
+	} else {
+		// No arguments, run the REPL
+		RunRepl()
+	}
+}

parser/ast.go

@@ -138,3 +138,21 @@ type GroupedExpression struct {
 
 func (ge *GroupedExpression) expressionNode()      {}
 func (ge *GroupedExpression) TokenLiteral() string { return ge.Token.Value }
+
+type IfExpression struct {
+	Token       lexer.Token // The 'if' token
+	Condition   Expression
+	Consequence *BlockStatement
+	Alternative *BlockStatement // nil if no 'else'
+}
+
+func (ie *IfExpression) expressionNode()      {}
+func (ie *IfExpression) TokenLiteral() string { return ie.Token.Value }
+
+type BooleanLiteral struct {
+	Token lexer.Token
+	Value bool
+}
+
+func (bl *BooleanLiteral) expressionNode()      {}
+func (bl *BooleanLiteral) TokenLiteral() string { return bl.Token.Value }

parser/parser.go

@@ -18,11 +18,17 @@ const (
 )
 
 var precedences = map[lexer.TokenType]int{
-	lexer.TokenPlus:        SUM,
-	lexer.TokenMinus:       SUM,
-	lexer.TokenStar:        PRODUCT,
-	lexer.TokenSlash:       PRODUCT,
-	lexer.TokenLeftBracket: INDEX,
+	lexer.TokenPlus:         SUM,
+	lexer.TokenMinus:        SUM,
+	lexer.TokenStar:         PRODUCT,
+	lexer.TokenSlash:        PRODUCT,
+	lexer.TokenLeftBracket:  INDEX,
+	lexer.TokenEqualEqual:   LOWEST + 1,
+	lexer.TokenNotEqual:     LOWEST + 1,
+	lexer.TokenLessThan:     LOWEST + 1,
+	lexer.TokenGreaterThan:  LOWEST + 1,
+	lexer.TokenLessEqual:    LOWEST + 1,
+	lexer.TokenGreaterEqual: LOWEST + 1,
 }
 
 type (
@@ -55,6 +61,9 @@ func New(l *lexer.Lexer) *Parser {
 	p.registerPrefix(lexer.TokenLeftBrace, p.parseTableLiteral)
 	p.registerPrefix(lexer.TokenMinus, p.parsePrefixExpression)
 	p.registerPrefix(lexer.TokenLeftParen, p.parseGroupedExpression)
+	p.registerPrefix(lexer.TokenIf, p.parseIfExpression)      // New
+	p.registerPrefix(lexer.TokenTrue, p.parseBooleanLiteral)  // New
+	p.registerPrefix(lexer.TokenFalse, p.parseBooleanLiteral) // New
 
 	// Initialize infix parse functions
 	p.infixParseFns = make(map[lexer.TokenType]infixParseFn)
@@ -64,6 +73,14 @@ func New(l *lexer.Lexer) *Parser {
 	p.registerInfix(lexer.TokenSlash, p.parseInfixExpression)
 	p.registerInfix(lexer.TokenLeftBracket, p.parseIndexExpression)
 
+	// Register comparison operators
+	p.registerInfix(lexer.TokenEqualEqual, p.parseInfixExpression)
+	p.registerInfix(lexer.TokenNotEqual, p.parseInfixExpression)
+	p.registerInfix(lexer.TokenLessThan, p.parseInfixExpression)
+	p.registerInfix(lexer.TokenGreaterThan, p.parseInfixExpression)
+	p.registerInfix(lexer.TokenLessEqual, p.parseInfixExpression)
+	p.registerInfix(lexer.TokenGreaterEqual, p.parseInfixExpression)
+
 	// Read two tokens, so curToken and peekToken are both set
 	p.nextToken()
 	p.nextToken()
@@ -415,3 +432,58 @@ func (p *Parser) parseGroupedExpression() Expression {
 		Expr:  exp,
 	}
 }
+
+func (p *Parser) parseBooleanLiteral() Expression {
+	return &BooleanLiteral{
+		Token: p.curToken,
+		Value: p.curTokenIs(lexer.TokenTrue),
+	}
+}
+
+func (p *Parser) parseIfExpression() Expression {
+	expression := &IfExpression{Token: p.curToken}
+
+	p.nextToken() // Skip 'if'
+
+	// Parse condition
+	expression.Condition = p.parseExpression(LOWEST)
+
+	if !p.expectPeek(lexer.TokenThen) {
+		return nil
+	}
+
+	p.nextToken() // Skip 'then'
+
+	// Parse consequence (then block)
+	if p.curTokenIs(lexer.TokenLeftBrace) {
+		expression.Consequence = p.parseBlockStatement()
+	} else {
+		// For single statement without braces
+		stmt := &BlockStatement{Token: p.curToken}
+		stmt.Statements = []Statement{p.parseStatement()}
+		expression.Consequence = stmt
+	}
+
+	// Check for 'else'
+	if p.peekTokenIs(lexer.TokenElse) {
+		p.nextToken() // Skip current token
+		p.nextToken() // Skip 'else'
+
+		// Parse alternative (else block)
+		if p.curTokenIs(lexer.TokenLeftBrace) {
+			expression.Alternative = p.parseBlockStatement()
+		} else {
+			// For single statement without braces
+			stmt := &BlockStatement{Token: p.curToken}
+			stmt.Statements = []Statement{p.parseStatement()}
+			expression.Alternative = stmt
+		}
+	}
+
+	// Check for 'end' if we had a then block without braces
+	if !p.curTokenIs(lexer.TokenRightBrace) && p.peekTokenIs(lexer.TokenEnd) {
+		p.nextToken() // Consume 'end'
+	}
+
+	return expression
+}

repl.go

@@ -1,45 +0,0 @@
-// File: cmd/main.go
-package main
-
-import (
-	"bufio"
-	"fmt"
-	"os"
-
-	"git.sharkk.net/Sharkk/Mako/compiler"
-	"git.sharkk.net/Sharkk/Mako/lexer"
-	"git.sharkk.net/Sharkk/Mako/parser"
-	"git.sharkk.net/Sharkk/Mako/vm"
-)
-
-func main() {
-	scanner := bufio.NewScanner(os.Stdin)
-	virtualMachine := vm.New()
-
-	fmt.Println("Mako REPL (type 'exit' to quit)")
-	for {
-		fmt.Print(">> ")
-		if !scanner.Scan() {
-			break
-		}
-
-		input := scanner.Text()
-		if input == "exit" {
-			break
-		}
-
-		lex := lexer.New(input)
-		p := parser.New(lex)
-		program := p.ParseProgram()
-
-		if len(p.Errors()) > 0 {
-			for _, err := range p.Errors() {
-				fmt.Printf("Error: %s\n", err)
-			}
-			continue
-		}
-
-		bytecode := compiler.Compile(program)
-		virtualMachine.Run(bytecode)
-	}
-}

types/types.go

@@ -31,6 +31,14 @@ const (
 	OpMultiply
 	OpDivide
 	OpNegate
+	OpJumpIfFalse
+	OpJump
+	OpEqual
+	OpNotEqual
+	OpLessThan
+	OpGreaterThan
+	OpLessEqual
+	OpGreaterEqual
 )
 
 type Instruction struct {
@@ -60,6 +68,10 @@ func NewNumber(n float64) Value {
 	return Value{Type: TypeNumber, Data: n}
 }
 
+func NewBoolean(b bool) Value {
+	return Value{Type: TypeBoolean, Data: b}
+}
+
 // TableEntry maintains insertion order
 type TableEntry struct {
 	Key   Value

vm/vm.go

@@ -44,6 +44,10 @@ func (vm *VM) Run(bytecode *types.Bytecode) {
 				vm.push(types.NewString(v))
 			case float64:
 				vm.push(types.NewNumber(v))
+			case bool:
+				vm.push(types.NewBoolean(v))
+			case nil:
+				vm.push(types.NewNull())
 			}
 
 		case types.OpSetLocal:
@@ -164,6 +168,27 @@ func (vm *VM) Run(bytecode *types.Bytecode) {
 				fmt.Println(vm.formatTable(value.Data.(*types.Table)))
 			}
 
+		// Jump instructions
+		case types.OpJumpIfFalse:
+			condition := vm.pop()
+			// Consider falsy: false, null, 0
+			shouldJump := false
+
+			if condition.Type == types.TypeBoolean && !condition.Data.(bool) {
+				shouldJump = true
+			} else if condition.Type == types.TypeNull {
+				shouldJump = true
+			} else if condition.Type == types.TypeNumber && condition.Data.(float64) == 0 {
+				shouldJump = true
+			}
+
+			if shouldJump {
+				ip = instruction.Operand - 1 // -1 because loop will increment
+			}
+
+		case types.OpJump:
+			ip = instruction.Operand - 1 // -1 because loop will increment
+
 		// Arithmetic operations
 		case types.OpAdd:
 			right := vm.pop()
@@ -233,16 +258,178 @@ func (vm *VM) Run(bytecode *types.Bytecode) {
 				fmt.Println("Error: cannot negate non-number value")
 				vm.push(types.NewNull())
 			}
+
+		// Comparison operators with safer implementation
+		case types.OpEqual:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for equality comparison")
+				vm.push(types.NewBoolean(false))
+				continue
+			}
+
+			right := vm.pop()
+			left := vm.pop()
+
+			if left.Type != right.Type {
+				vm.push(types.NewBoolean(false))
+			} else {
+				switch left.Type {
+				case types.TypeNumber:
+					vm.push(types.NewBoolean(left.Data.(float64) == right.Data.(float64)))
+				case types.TypeString:
+					vm.push(types.NewBoolean(left.Data.(string) == right.Data.(string)))
+				case types.TypeBoolean:
+					vm.push(types.NewBoolean(left.Data.(bool) == right.Data.(bool)))
+				case types.TypeNull:
+					vm.push(types.NewBoolean(true)) // null == null
+				default:
+					vm.push(types.NewBoolean(false))
+				}
+			}
+
+		case types.OpNotEqual:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for inequality comparison")
+				vm.push(types.NewBoolean(true))
+				continue
+			}
+
+			right := vm.pop()
+			left := vm.pop()
+
+			if left.Type != right.Type {
+				vm.push(types.NewBoolean(true))
+			} else {
+				switch left.Type {
+				case types.TypeNumber:
+					vm.push(types.NewBoolean(left.Data.(float64) != right.Data.(float64)))
+				case types.TypeString:
+					vm.push(types.NewBoolean(left.Data.(string) != right.Data.(string)))
+				case types.TypeBoolean:
+					vm.push(types.NewBoolean(left.Data.(bool) != right.Data.(bool)))
+				case types.TypeNull:
+					vm.push(types.NewBoolean(false)) // null != null is false
+				default:
+					vm.push(types.NewBoolean(true))
+				}
+			}
+
+		case types.OpLessThan:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for less-than comparison")
+				vm.push(types.NewBoolean(false))
+				continue
+			}
+
+			// Peek at values first before popping
+			right := vm.stack[vm.sp-1]
+			left := vm.stack[vm.sp-2]
+
+			if left.Type == types.TypeNumber && right.Type == types.TypeNumber {
+				// Now pop them
+				vm.pop()
+				vm.pop()
+				vm.push(types.NewBoolean(left.Data.(float64) < right.Data.(float64)))
+			} else {
+				// Pop the values to maintain stack balance
+				vm.pop()
+				vm.pop()
+				fmt.Println("Error: cannot compare non-number values with <")
+				vm.push(types.NewBoolean(false))
+			}
+
+		case types.OpGreaterThan:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for greater-than comparison")
+				vm.push(types.NewBoolean(false))
+				continue
+			}
+
+			// Peek at values first before popping
+			right := vm.stack[vm.sp-1]
+			left := vm.stack[vm.sp-2]
+
+			if left.Type == types.TypeNumber && right.Type == types.TypeNumber {
+				// Now pop them
+				vm.pop()
+				vm.pop()
+				vm.push(types.NewBoolean(left.Data.(float64) > right.Data.(float64)))
+			} else {
+				// Pop the values to maintain stack balance
+				vm.pop()
+				vm.pop()
+				fmt.Println("Error: cannot compare non-number values with >")
+				vm.push(types.NewBoolean(false))
+			}
+
+		case types.OpLessEqual:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for less-equal comparison")
+				vm.push(types.NewBoolean(false))
+				continue
+			}
+
+			// Peek at values first before popping
+			right := vm.stack[vm.sp-1]
+			left := vm.stack[vm.sp-2]
+
+			if left.Type == types.TypeNumber && right.Type == types.TypeNumber {
+				// Now pop them
+				vm.pop()
+				vm.pop()
+				vm.push(types.NewBoolean(left.Data.(float64) <= right.Data.(float64)))
+			} else {
+				// Pop the values to maintain stack balance
+				vm.pop()
+				vm.pop()
+				fmt.Println("Error: cannot compare non-number values with <=")
+				vm.push(types.NewBoolean(false))
+			}
+
+		case types.OpGreaterEqual:
+			if vm.sp < 2 {
+				fmt.Println("Error: not enough operands for greater-equal comparison")
+				vm.push(types.NewBoolean(false))
+				continue
+			}
+
+			// Peek at values first before popping
+			right := vm.stack[vm.sp-1]
+			left := vm.stack[vm.sp-2]
+
+			if left.Type == types.TypeNumber && right.Type == types.TypeNumber {
+				// Now pop them
+				vm.pop()
+				vm.pop()
+				vm.push(types.NewBoolean(left.Data.(float64) >= right.Data.(float64)))
+			} else {
+				// Pop the values to maintain stack balance
+				vm.pop()
+				vm.pop()
+				fmt.Println("Error: cannot compare non-number values with >=")
+				vm.push(types.NewBoolean(false))
+			}
 		}
 	}
 }
 
 func (vm *VM) push(value types.Value) {
+	if vm.sp >= len(vm.stack) {
+		// Grow stack if needed
+		newStack := make([]types.Value, len(vm.stack)*2)
+		copy(newStack, vm.stack)
+		vm.stack = newStack
+	}
 	vm.stack[vm.sp] = value
 	vm.sp++
 }
 
 func (vm *VM) pop() types.Value {
+	if vm.sp <= 0 {
+		// Return null instead of causing a panic when trying to pop from an empty stack
+		fmt.Println("Stack underflow error")
+		return types.NewNull()
+	}
 	vm.sp--
 	return vm.stack[vm.sp]
 }