Add print and expression statements

.task/checksum/astgen

@@ -1 +1 @@
-f630c7b1cf9f3b55f1467ac4c8704152
+bf6f2cc6973975f2bcc789463842856a

Taskfile.yml

@@ -26,7 +26,7 @@ tasks:
     desc: "Run tests"
     deps: [astgen]
     cmds:
-      - go test -v ./...
+      - go test ./... {{.CLI_ARGS}}
 
   astgen:
     desc: "Generate AST nodes"
@@ -36,6 +36,7 @@ tasks:
       - cmd/astgen/main.go
     generates:
       - ast/expr.go
+      - ast/stmt.go
 
   clean:
     desc: "Clean up"

ast/expr.go

@@ -3,11 +3,11 @@ package ast
 import "golox/token"
 
 type ExprVisitor[T any] interface {
-	VisitErrorExpr(error *ErrorExpr) T
-	VisitBinaryExpr(binary *BinaryExpr) T
-	VisitGroupingExpr(grouping *GroupingExpr) T
-	VisitLiteralExpr(literal *LiteralExpr) T
-	VisitUnaryExpr(unary *UnaryExpr) T
+	VisitErrorExpr(ee *ErrorExpr) T
+	VisitBinaryExpr(be *BinaryExpr) T
+	VisitGroupingExpr(ge *GroupingExpr) T
+	VisitLiteralExpr(le *LiteralExpr) T
+	VisitUnaryExpr(ue *UnaryExpr) T
 }
 
 type Expr interface {
@@ -18,8 +18,8 @@ type ErrorExpr struct {
 	Value string
 }
 
-func (t *ErrorExpr) Accept(visitor ExprVisitor[any]) any {
-	return visitor.VisitErrorExpr(t)
+func (ee *ErrorExpr) Accept(v ExprVisitor[any]) any {
+	return v.VisitErrorExpr(ee)
 }
 
 type BinaryExpr struct {
@@ -28,24 +28,24 @@ type BinaryExpr struct {
 	Right Expr
 }
 
-func (t *BinaryExpr) Accept(visitor ExprVisitor[any]) any {
-	return visitor.VisitBinaryExpr(t)
+func (be *BinaryExpr) Accept(v ExprVisitor[any]) any {
+	return v.VisitBinaryExpr(be)
 }
 
 type GroupingExpr struct {
 	Expression Expr
 }
 
-func (t *GroupingExpr) Accept(visitor ExprVisitor[any]) any {
-	return visitor.VisitGroupingExpr(t)
+func (ge *GroupingExpr) Accept(v ExprVisitor[any]) any {
+	return v.VisitGroupingExpr(ge)
 }
 
 type LiteralExpr struct {
 	Value any
 }
 
-func (t *LiteralExpr) Accept(visitor ExprVisitor[any]) any {
-	return visitor.VisitLiteralExpr(t)
+func (le *LiteralExpr) Accept(v ExprVisitor[any]) any {
+	return v.VisitLiteralExpr(le)
 }
 
 type UnaryExpr struct {
@@ -53,7 +53,7 @@ type UnaryExpr struct {
 	Right Expr
 }
 
-func (t *UnaryExpr) Accept(visitor ExprVisitor[any]) any {
-	return visitor.VisitUnaryExpr(t)
+func (ue *UnaryExpr) Accept(v ExprVisitor[any]) any {
+	return v.VisitUnaryExpr(ue)
 }
 

ast/printer.go

@@ -11,10 +11,36 @@ func NewPrinter() *Printer {
 	return &Printer{}
 }
 
-func (ap *Printer) Print(expr Expr) string {
+func (ap *Printer) PrintStmts(stmts []Stmt) string {
+	str := ""
+
+	for _, stmt := range stmts {
+		str += stmt.Accept(ap).(string) + "\n"
+	}
+
+	return str
+}
+
+func (ap *Printer) PrintExpr(expr Expr) string {
 	return expr.Accept(ap).(string)
 }
 
+func (ap *Printer) VisitErrorStmt(stmt *ErrorStmt) any {
+	return stmt.Value
+}
+
+func (ap *Printer) VisitExpressionStmt(stmt *ExpressionStmt) any {
+	return stmt.Expression.Accept(ap)
+}
+
+func (ap *Printer) VisitPrintStmt(stmt *PrintStmt) any {
+	return ap.parenthesize("print", stmt.Expression)
+}
+
+func (ap *Printer) VisitVarStmt(stmt *VarStmt) any {
+	return ap.parenthesize("var", &LiteralExpr{stmt.Name}, stmt.Initializer)
+}
+
 func (ap *Printer) VisitBinaryExpr(expr *BinaryExpr) any {
 	return ap.parenthesize(expr.Operator.Lexeme, expr.Left, expr.Right)
 }

ast/printer_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 )
 
-func TestPrinter(t *testing.T) {
+func TestPrintExpr(t *testing.T) {
 	tests := []struct {
 		name     string
 		expr     Expr
@@ -55,7 +55,44 @@ func TestPrinter(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			printer := NewPrinter()
-			result := printer.Print(tt.expr)
+			result := printer.PrintExpr(tt.expr)
+			if result != tt.expected {
+				t.Errorf("expected %v, got %v", tt.expected, result)
+			}
+		})
+	}
+}
+
+func TestPrintStmts(t *testing.T) {
+	tests := []struct {
+		name     string
+		stmts    []Stmt
+		expected string
+	}{
+		{
+			name: "Print statement",
+			stmts: []Stmt{
+				&PrintStmt{
+					Expression: &LiteralExpr{Value: 42},
+				},
+			},
+			expected: "(print 42)\n",
+		},
+		{
+			name: "Expression statement",
+			stmts: []Stmt{
+				&ExpressionStmt{
+					Expression: &LiteralExpr{Value: 42},
+				},
+			},
+			expected: "42\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			printer := NewPrinter()
+			result := printer.PrintStmts(tt.stmts)
 			if result != tt.expected {
 				t.Errorf("expected %v, got %v", tt.expected, result)
 			}

ast/stmt.go

@@ -0,0 +1,48 @@
+package ast
+
+import "golox/token"
+
+type StmtVisitor[T any] interface {
+	VisitErrorStmt(es *ErrorStmt) T
+	VisitExpressionStmt(es *ExpressionStmt) T
+	VisitPrintStmt(ps *PrintStmt) T
+	VisitVarStmt(vs *VarStmt) T
+}
+
+type Stmt interface {
+	Accept(visitor StmtVisitor[any]) any
+}
+
+type ErrorStmt struct {
+	Value string
+}
+
+func (es *ErrorStmt) Accept(v StmtVisitor[any]) any {
+	return v.VisitErrorStmt(es)
+}
+
+type ExpressionStmt struct {
+	Expression Expr
+}
+
+func (es *ExpressionStmt) Accept(v StmtVisitor[any]) any {
+	return v.VisitExpressionStmt(es)
+}
+
+type PrintStmt struct {
+	Expression Expr
+}
+
+func (ps *PrintStmt) Accept(v StmtVisitor[any]) any {
+	return v.VisitPrintStmt(ps)
+}
+
+type VarStmt struct {
+	Name token.Token
+	Initializer Expr
+}
+
+func (vs *VarStmt) Accept(v StmtVisitor[any]) any {
+	return v.VisitVarStmt(vs)
+}
+

cmd/astgen/main.go

@@ -28,6 +28,13 @@ func main() {
 		"Literal  : Value any",
 		"Unary    : Operator token.Token, Right Expr",
 	})
+
+	defineAst(d, "Stmt", []string{
+		"Error        : Value string",
+		"Expression   : Expression Expr",
+		"Print        : Expression Expr",
+		"Var          : Name token.Token, Initializer Expr",
+	})
 }
 
 func defineAst(outputDir, baseName string, types []string) {
@@ -58,7 +65,8 @@ func defineVisitor(file *os.File, baseName string, types []string) {
 
 	for _, t := range types {
 		typeName := strings.TrimSpace(t[:strings.Index(t, ":")-1])
-		file.WriteString("	Visit" + typeName + baseName + "(" + strings.ToLower(typeName) + " *" + typeName + baseName + ") T\n")
+		paramName := strings.ToLower(typeName[:1]) + strings.ToLower(baseName[:1])
+		file.WriteString("	Visit" + typeName + baseName + "(" + paramName + " *" + typeName + baseName + ") T\n")
 	}
 
 	file.WriteString("}\n\n")
@@ -74,8 +82,9 @@ func defineType(file *os.File, baseName, typeString string) {
 		file.WriteString("	" + field + "\n")
 	}
 
+	varName := strings.ToLower(typeName[:1]) + strings.ToLower(baseName[:1])
 	file.WriteString("}\n\n")
-	file.WriteString("func (t *" + typeName + baseName + ") Accept(visitor " + baseName + "Visitor[any]) any {\n")
-	file.WriteString("	return visitor.Visit" + typeName + baseName + "(t)\n")
+	file.WriteString("func (" + varName + " *" + typeName + baseName + ") Accept(v " + baseName + "Visitor[any]) any {\n")
+	file.WriteString("	return v.Visit" + typeName + baseName + "(" + varName + ")\n")
 	file.WriteString("}\n\n")
 }

interpreter/interpreter.go

@@ -14,8 +14,40 @@ type Interpreter struct {
 }
 
 // New creates a new Interpreter.
-func New() *Interpreter {
-	return &Interpreter{}
+func New(el errors.Logger) *Interpreter {
+	return &Interpreter{el}
+}
+
+// Interpret interprets the AST.
+func (i *Interpreter) Interpret(stmts []ast.Stmt) {
+	defer i.afterPanic()
+
+	for _, stmt := range stmts {
+		i.execute(stmt)
+	}
+}
+
+// VisitErrorStmt visits an error statement.
+func (i *Interpreter) VisitErrorStmt(es *ast.ErrorStmt) any {
+	panic(es.Value)
+}
+
+// VisitExpressionStmt visits an expression.
+func (i *Interpreter) VisitExpressionStmt(es *ast.ExpressionStmt) any {
+	i.evaluate(es.Expression)
+	return nil
+}
+
+// VisitPrintStmt visits a print statement.
+func (i *Interpreter) VisitPrintStmt(ps *ast.PrintStmt) any {
+	value := i.evaluate(ps.Expression)
+	fmt.Println(stringify(value))
+	return nil
+}
+
+// VisitVarStmt visits a var statement.
+func (i *Interpreter) VisitVarStmt(vs *ast.VarStmt) any {
+	return nil
 }
 
 // Interpret interprets the AST.
@@ -150,6 +182,11 @@ func (i *Interpreter) evaluate(e ast.Expr) any {
 	return e.Accept(i)
 }
 
+// execute executes a statement.
+func (i *Interpreter) execute(s ast.Stmt) {
+	s.Accept(i)
+}
+
 // stringify returns a string representation of a value.
 func stringify(v any) string {
 	if v == nil {

interpreter/interpreter_test.go

@@ -3,13 +3,14 @@ package interpreter_test
 
 import (
 	"golox/ast"
+	"golox/errors"
 	"golox/interpreter"
 	"golox/token"
 	"testing"
 )
 
 func TestInterpretLiteralExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	literal := &ast.LiteralExpr{Value: 42}
 
 	result := i.VisitLiteralExpr(literal)
@@ -19,7 +20,7 @@ func TestInterpretLiteralExpr(t *testing.T) {
 }
 
 func TestInterpretGroupingExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	literal := &ast.LiteralExpr{Value: 42}
 	grouping := &ast.GroupingExpr{Expression: literal}
 
@@ -30,7 +31,7 @@ func TestInterpretGroupingExpr(t *testing.T) {
 }
 
 func TestInterpretUnaryExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	literal := &ast.LiteralExpr{Value: 42.0}
 	unary := &ast.UnaryExpr{
 		Operator: token.Token{Type: token.MINUS, Lexeme: "-"},
@@ -44,7 +45,7 @@ func TestInterpretUnaryExpr(t *testing.T) {
 }
 
 func TestInterpretUnaryExprBang(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	literal := &ast.LiteralExpr{Value: true}
 	unary := &ast.UnaryExpr{
 		Operator: token.Token{Type: token.BANG, Lexeme: "!"},
@@ -58,7 +59,7 @@ func TestInterpretUnaryExprBang(t *testing.T) {
 }
 
 func TestInterpretErrorExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	errorExpr := &ast.ErrorExpr{Value: "error"}
 
 	defer func() {
@@ -71,7 +72,7 @@ func TestInterpretErrorExpr(t *testing.T) {
 }
 
 func TestInterpretExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	literal := &ast.LiteralExpr{Value: 42.0}
 
 	defer func() {
@@ -87,7 +88,7 @@ func TestInterpretExpr(t *testing.T) {
 }
 
 func TestInterpretBinaryExpr(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{
@@ -103,7 +104,7 @@ func TestInterpretBinaryExpr(t *testing.T) {
 }
 
 func TestInterpretBinaryExprDivisionByZero(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 0.0}
 	binary := &ast.BinaryExpr{
@@ -122,7 +123,7 @@ func TestInterpretBinaryExprDivisionByZero(t *testing.T) {
 }
 
 func TestInterpretBinaryExprAddition(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{
@@ -138,7 +139,7 @@ func TestInterpretBinaryExprAddition(t *testing.T) {
 }
 
 func TestInterpretBinaryExprSubtraction(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{
@@ -154,7 +155,7 @@ func TestInterpretBinaryExprSubtraction(t *testing.T) {
 }
 
 func TestInterpretBinaryExprStringConcatenation(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: "foo"}
 	right := &ast.LiteralExpr{Value: "bar"}
 	binary := &ast.BinaryExpr{
@@ -170,7 +171,7 @@ func TestInterpretBinaryExprStringConcatenation(t *testing.T) {
 }
 
 func TestInterpretBinaryExprInvalidOperands(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: "foo"}
 	right := &ast.LiteralExpr{Value: 42.0}
 	binary := &ast.BinaryExpr{
@@ -189,7 +190,7 @@ func TestInterpretBinaryExprInvalidOperands(t *testing.T) {
 }
 
 func TestInterpretBinaryExprComparison(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{
@@ -205,7 +206,7 @@ func TestInterpretBinaryExprComparison(t *testing.T) {
 }
 
 func TestInterpretBinaryExprComparisonEqual(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 42.0}
 	binary := &ast.BinaryExpr{
@@ -221,7 +222,7 @@ func TestInterpretBinaryExprComparisonEqual(t *testing.T) {
 }
 
 func TestInterpretBinaryExprComparisonNotEqual(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{
@@ -237,7 +238,7 @@ func TestInterpretBinaryExprComparisonNotEqual(t *testing.T) {
 }
 
 func TestInterpretBinaryExprComparisonInvalidOperands(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: "foo"}
 	right := &ast.LiteralExpr{Value: 42.0}
 	binary := &ast.BinaryExpr{
@@ -256,7 +257,7 @@ func TestInterpretBinaryExprComparisonInvalidOperands(t *testing.T) {
 }
 
 func TestInterpretBinaryExprInvalidOperatorType(t *testing.T) {
-	i := interpreter.New()
+	i := interpreter.New(errors.NewMockErrorLogger())
 	left := &ast.LiteralExpr{Value: 42.0}
 	right := &ast.LiteralExpr{Value: 2.0}
 	binary := &ast.BinaryExpr{

lox/lox.go

@@ -17,11 +17,14 @@ type Lox struct {
 }
 
 func New() *Lox {
-	return &Lox{
+	l := &Lox{
 		hadError:        false,
 		hadRuntimeError: false,
-		interpreter:     interpreter.New(),
 	}
+
+	l.interpreter = interpreter.New(l)
+
+	return l
 }
 
 func (l *Lox) RunFile(path string) {
@@ -90,12 +93,12 @@ func (l *Lox) run(source string) {
 	scanner := scanner.New(source, l)
 	tokens := scanner.ScanTokens()
 	parser := parser.New(tokens, l)
-	expr := parser.Parse()
+	stmts := parser.Parse()
 
+	// Stop if there was a syntax error.
 	if l.hadError {
 		return
 	}
 
-	s := l.interpreter.InterpretExpr(expr)
-	fmt.Println(s)
+	l.interpreter.Interpret(stmts)
 }

lox/lox_test.go

@@ -24,7 +24,7 @@ func TestRun(t *testing.T) {
 		outC <- buf.String()
 	}()
 
-	source := "1+4/2"
+	source := "print 1+4/2;"
 	l := New()
 	l.run(source)
 
@@ -63,7 +63,7 @@ func TestRunFile(t *testing.T) {
 	}
 	defer os.Remove(tmpfile.Name())
 
-	content := "1+4/2"
+	content := "print 1+4/2;"
 	if _, err := tmpfile.Write([]byte(content)); err != nil {
 		t.Fatal(err)
 	}
@@ -166,7 +166,7 @@ func TestRunPrompt(t *testing.T) {
 		outC <- buf.String()
 	}()
 
-	input := "1+4/2\n\n"
+	input := "print 1+4/2;\n\n"
 	wIn.Write([]byte(input))
 	wIn.Close()
 

parser/parser.go

@@ -2,6 +2,11 @@
  * The parser is responsible for parsing the tokens generated by the scanner.
  *
  * The grammar is as follows:
+ * program        → statement* EOF ;
+ * statement      → exprStmt
+ *                | printStmt ;
+ * exprStmt       → expression ";" ;
+ * printStmt      → "print" expression ";" ;
  * expression     → equality ;
  * equality       → comparison ( ( "!=" | "==" ) comparison )* ;
  * comparison     → term ( ( ">" | ">=" | "<" | "<=" ) term )* ;
@@ -33,8 +38,50 @@ func New(tokens []token.Token, el errors.Logger) *Parser {
 }
 
 // Parse parses the tokens and returns the AST.
-func (p *Parser) Parse() ast.Expr {
-	return p.expression()
+func (p *Parser) Parse() []ast.Stmt {
+	stmts := []ast.Stmt{}
+
+	for !p.isAtEnd() {
+		stmt := p.statement()
+		if _, ok := stmt.(*ast.ErrorStmt); ok {
+			p.synchronize()
+		} else {
+			stmts = append(stmts, stmt)
+		}
+	}
+
+	return stmts
+}
+
+// statement → exprStmt | printStmt ;
+func (p *Parser) statement() ast.Stmt {
+	if p.match(token.PRINT) {
+		return p.printStatement()
+	}
+
+	return p.expressionStatement()
+}
+
+// exprStmt → expression ";" ;
+func (p *Parser) expressionStatement() ast.Stmt {
+	expr := p.expression()
+	err := p.consume(token.SEMICOLON, "Expect ';' after expression.")
+	if err != nil {
+		return p.fromErrorExpr(err)
+	}
+
+	return &ast.ExpressionStmt{Expression: expr}
+}
+
+// printStmt → "print" expression ";" ;
+func (p *Parser) printStatement() ast.Stmt {
+	expr := p.expression()
+	err := p.consume(token.SEMICOLON, "Expect ';' after value.")
+	if err != nil {
+		return p.fromErrorExpr(err)
+	}
+
+	return &ast.PrintStmt{Expression: expr}
 }
 
 // expression → equality ;
@@ -189,7 +236,13 @@ func (p *Parser) newErrorExpr(t token.Token, message string) *ast.ErrorExpr {
 	return &ast.ErrorExpr{Value: message}
 }
 
+// fromErrorExpr creates an ErrorStmt from an ErrorExpr.
+func (p *Parser) fromErrorExpr(ee *ast.ErrorExpr) *ast.ErrorStmt {
+	return &ast.ErrorStmt{Value: ee.Value}
+}
+
 // synchronize synchronizes the parser after an error.
+// It skips tokens until it finds a statement boundary.
 func (p *Parser) synchronize() {
 	p.advance()
 

parser/parser_test.go

@@ -7,7 +7,7 @@ import (
 	"testing"
 )
 
-func TestParser(t *testing.T) {
+func TestExpressionParsing(t *testing.T) {
 	tests := []struct {
 		name     string
 		tokens   []token.Token
@@ -19,6 +19,7 @@ func TestParser(t *testing.T) {
 				{Type: token.NUMBER, Literal: 1},
 				{Type: token.PLUS, Lexeme: "+"},
 				{Type: token.NUMBER, Literal: 2},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "(+ 1 2)",
@@ -28,6 +29,7 @@ func TestParser(t *testing.T) {
 			tokens: []token.Token{
 				{Type: token.MINUS, Lexeme: "-"},
 				{Type: token.NUMBER, Literal: 123},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "(- 123)",
@@ -40,6 +42,7 @@ func TestParser(t *testing.T) {
 				{Type: token.PLUS, Lexeme: "+"},
 				{Type: token.NUMBER, Literal: 2},
 				{Type: token.RIGHT_PAREN, Lexeme: ")"},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "(group (+ 1 2))",
@@ -50,6 +53,7 @@ func TestParser(t *testing.T) {
 				{Type: token.NUMBER, Literal: 1},
 				{Type: token.GREATER, Lexeme: ">"},
 				{Type: token.NUMBER, Literal: 2},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "(> 1 2)",
@@ -60,6 +64,7 @@ func TestParser(t *testing.T) {
 				{Type: token.NUMBER, Literal: 1},
 				{Type: token.EQUAL_EQUAL, Lexeme: "=="},
 				{Type: token.NUMBER, Literal: 2},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "(== 1 2)",
@@ -71,6 +76,7 @@ func TestParser(t *testing.T) {
 				{Type: token.NUMBER, Literal: 1},
 				{Type: token.PLUS, Lexeme: "+"},
 				{Type: token.NUMBER, Literal: 2},
+				{Type: token.SEMICOLON, Lexeme: ";"},
 				{Type: token.EOF},
 			},
 			expected: "Expect ')' after expression.",
@@ -80,9 +86,90 @@ func TestParser(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			parser := New(tt.tokens, errors.NewMockErrorLogger())
-			expr := parser.Parse()
+			stmts := parser.Parse()
+			if len(stmts) != 1 {
+				t.Fatalf("expected 1 statement, got %d", len(stmts))
+			}
+
+			stmt := stmts[0]
+			var expr ast.Expr
+			if es, ok := stmt.(*ast.ExpressionStmt); !ok {
+				t.Errorf("expected ExprStmt, got %T", stmt)
+			} else {
+				expr = es.Expression
+			}
+
+			ap := ast.NewPrinter()
+			s := ap.PrintExpr(expr)
+			if s != tt.expected {
+				t.Errorf("expected %v, got %v", tt.expected, s)
+			}
+		})
+	}
+}
+
+func TestParseExpressionStmt(t *testing.T) {
+	tests := []struct {
+		name     string
+		tokens   []token.Token
+		expected string
+	}{
+		{
+			name: "simple expression statement",
+			tokens: []token.Token{
+				{Type: token.NUMBER, Lexeme: "42", Literal: 42},
+				{Type: token.SEMICOLON, Lexeme: ";"},
+				{Type: token.EOF},
+			},
+			expected: "42\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			parser := New(tt.tokens, errors.NewMockErrorLogger())
+			stmts := parser.Parse()
+			if len(stmts) != 1 {
+				t.Fatalf("expected 1 statement, got %d", len(stmts))
+			}
+
+			ap := ast.NewPrinter()
+			s := ap.PrintStmts(stmts)
+			if s != tt.expected {
+				t.Errorf("expected %v, got %v", tt.expected, s)
+			}
+		})
+	}
+}
+
+func TestParsePrintStmt(t *testing.T) {
+	tests := []struct {
+		name     string
+		tokens   []token.Token
+		expected string
+	}{
+		{
+			name: "simple print statement",
+			tokens: []token.Token{
+				{Type: token.PRINT, Lexeme: "print"},
+				{Type: token.NUMBER, Lexeme: "42", Literal: 42},
+				{Type: token.SEMICOLON, Lexeme: ";"},
+				{Type: token.EOF},
+			},
+			expected: "(print 42)\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			parser := New(tt.tokens, errors.NewMockErrorLogger())
+			stmts := parser.Parse()
+			if len(stmts) != 1 {
+				t.Fatalf("expected 1 statement, got %d", len(stmts))
+			}
+
 			ap := ast.NewPrinter()
-			s := ap.Print(expr)
+			s := ap.PrintStmts(stmts)
 			if s != tt.expected {
 				t.Errorf("expected %v, got %v", tt.expected, s)
 			}