class statement

.vscode/settings.json

@@ -1,5 +1,6 @@
 {
     "cSpell.words": [
+        "arity",
         "glox",
         "PAREN",
         "stmts"

ast_string.go

@@ -71,6 +71,43 @@ func (as *AstStringer) visitLogical(l *Logical) any {
 	return nil
 }
 
+func (as *AstStringer) visitCall(c *Call) any {
+	as.str.WriteString("(call ")
+	c.callee.accept(as)
+	if len(c.args) != 0 {
+		as.str.WriteString(" ")
+	}
+	for i, arg := range c.args {
+		arg.accept(as)
+		if i < len(c.args)-1 {
+			as.str.WriteString(" ")
+		}
+	}
+	as.str.WriteString(")")
+
+	return nil
+}
+
+func (as *AstStringer) visitLambda(l *Lambda) any {
+	as.str.WriteString("(lambda ")
+	if len(l.args) != 0 {
+		as.str.WriteString("(")
+		for i, arg := range l.args {
+			as.str.WriteString(arg.lexeme)
+			if i < len(l.args)-1 {
+				as.str.WriteString(" ")
+			}
+		}
+		as.str.WriteString(")")
+	}
+	for _, stmt := range l.body {
+		stmt.accept(as)
+	}
+	as.str.WriteString(")")
+
+	return nil
+}
+
 func (as *AstStringer) visitPrintStmt(p *PrintStmt) {
 	as.str.WriteString("(print ")
 	p.val.accept(as)
@@ -104,7 +141,7 @@ func (as *AstStringer) visitBlockStmt(b *BlockStmt) {
 
 func (as *AstStringer) visitIfStmt(i *IfStmt) {
 	as.str.WriteString("(if ")
-	i.expr.accept(as)
+	i.cond.accept(as)
 	as.str.WriteString(" ")
 	i.then.accept(as)
 	if i.or != nil {
@@ -125,3 +162,35 @@ func (as *AstStringer) visitWhileStmt(w *WhileStmt) {
 	w.body.accept(as)
 	as.str.WriteString(")")
 }
+
+func (as *AstStringer) visitBreakStmt(b *BreakStmt) {
+	as.str.WriteString("(break)")
+}
+
+func (as *AstStringer) visitFunStmt(f *FunStmt) {
+	as.str.WriteString(fmt.Sprintf("(fun %s ", f.name.lexeme))
+	if len(f.args) != 0 {
+		as.str.WriteString("(")
+		for i, arg := range f.args {
+			as.str.WriteString(arg.lexeme)
+			if i < len(f.args)-1 {
+				as.str.WriteString(" ")
+			}
+		}
+		as.str.WriteString(")")
+	}
+	for _, stmt := range f.body {
+		stmt.accept(as)
+	}
+	as.str.WriteString(")")
+}
+
+func (as *AstStringer) visitReturnStmt(r *ReturnStmt) {
+	as.str.WriteString("(return ")
+	r.value.accept(as)
+	as.str.WriteString(")")
+}
+
+func (as *AstStringer) visitClassStmt(c *ClassStmt) {
+	fmt.Printf("(class %s)", c.name.lexeme)
+}

callable.go

@@ -0,0 +1,46 @@
+package main
+
+type Callable interface {
+	arity() int
+	call(i *Interpreter, args ...any) (ret any)
+}
+
+type Function struct {
+	name    Token
+	args    []Token
+	body    []Stmt
+	closure *Environment
+}
+
+func (f *Function) call(i *Interpreter, args ...any) (ret any) {
+
+	defer func() {
+		if err := recover(); err != nil {
+			re, ok := err.(Return)
+
+			if !ok {
+				panic(err)
+			}
+
+			ret = re.val
+		}
+	}()
+
+	env := newEnvironment(f.closure)
+
+	for idx, arg := range f.args {
+		env.define(arg.lexeme, args[idx])
+	}
+
+	i.executeBlock(f.body, env)
+
+	return nil
+}
+
+func (f *Function) arity() int {
+	return len(f.args)
+}
+
+func newFunction(name Token, args []Token, body []Stmt, env *Environment) Callable {
+	return &Function{name, args, body, env}
+}

class.go

@@ -0,0 +1,9 @@
+package main
+
+type Class struct {
+	name string
+}
+
+func (c *Class) String() string {
+	return c.name
+}

env.go

@@ -1,12 +1,14 @@
 package main
 
+import "fmt"
+
 type Environment struct {
-	values map[string]any
-	parent *Environment
+	values    map[string]any
+	enclosing *Environment
 }
 
-func newEnvironment(parent *Environment) *Environment {
-	return &Environment{values: map[string]any{}, parent: parent}
+func newEnvironment(enclosing *Environment) *Environment {
+	return &Environment{map[string]any{}, enclosing}
 }
 
 func (env *Environment) get(key string) any {
@@ -14,8 +16,8 @@ func (env *Environment) get(key string) any {
 		return found
 	}
 
-	if env.parent != nil {
-		return env.parent.get(key)
+	if env.enclosing != nil {
+		return env.enclosing.get(key)
 	}
 
 	return nil
@@ -23,20 +25,39 @@ func (env *Environment) get(key string) any {
 
 func (env *Environment) exists(key string) bool {
 	_, ok := env.values[key]
-
-	if !ok && env.parent != nil {
-		return env.parent.exists(key)
-	}
-
 	return ok
-
 }
 
-func (env *Environment) set(key string, val any) {
-
-	if env.parent != nil && env.parent.exists(key) {
-		env.parent.set(key, val)
-	}
-
+func (env *Environment) define(key string, val any) {
 	env.values[key] = val
 }
+
+func (env *Environment) assign(key Token, val any) *RuntimeError {
+	if env.exists(key.lexeme) {
+		env.values[key.lexeme] = val
+		return nil
+	}
+
+	if env.enclosing == nil {
+		return &RuntimeError{key, fmt.Sprintf("Can't assign: undefined variable '%s'.", key.lexeme)}
+	}
+
+	return env.enclosing.assign(key, val)
+}
+
+func (env *Environment) getAt(distance int, key string) any {
+	return env.ancestor(distance).get(key)
+}
+
+func (env *Environment) assignAt(distance int, key Token, val any) {
+	env.ancestor(distance).values[key.lexeme] = val
+}
+
+func (env *Environment) ancestor(distance int) *Environment {
+	parent := env
+	for i := 0; i < distance; i++ {
+		parent = parent.enclosing
+	}
+
+	return parent
+}

expr.go

@@ -1,7 +1,9 @@
 package main
 
 type ExprVisitor interface {
+	visitCall(c *Call) any
 	visitUnary(u *Unary) any
+	visitLambda(l *Lambda) any
 	visitBinary(b *Binary) any
 	visitLiteral(l *Literal) any
 	visitGrouping(g *Grouping) any
@@ -49,9 +51,23 @@ type Logical struct {
 	right    Expr
 }
 
+type Call struct {
+	callee Expr
+	paren  Token
+	args   []Expr
+}
+
+type Lambda struct {
+	name Token
+	args []Token
+	body []Stmt
+}
+
+func (c *Call) expr()     {}
 func (u *Unary) expr()    {}
 func (a *Assign) expr()   {}
 func (b *Binary) expr()   {}
+func (l *Lambda) expr()   {}
 func (l *Literal) expr()  {}
 func (g *Grouping) expr() {}
 func (v *Variable) expr() {}
@@ -84,3 +100,11 @@ func (a *Assign) accept(v ExprVisitor) any {
 func (l *Logical) accept(v ExprVisitor) any {
 	return v.visitLogical(l)
 }
+
+func (c *Call) accept(v ExprVisitor) any {
+	return v.visitCall(c)
+}
+
+func (l *Lambda) accept(v ExprVisitor) any {
+	return v.visitLambda(l)
+}

expr_rpn.go

@@ -1,63 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"strings"
-)
-
-type ExprToRPN struct {
-	str strings.Builder
-}
-
-func (as ExprToRPN) String(expr Expr) string {
-
-	if expr == nil {
-		return ""
-	}
-
-	expr.accept(&as)
-	return as.str.String()
-}
-
-func (as *ExprToRPN) visitBinary(b *Binary) any {
-	b.left.accept(as)
-	as.str.WriteString(" ")
-	b.right.accept(as)
-	as.str.WriteString(" ")
-	as.str.WriteString(b.op.lexeme)
-	return nil
-}
-
-func (as *ExprToRPN) visitLiteral(l *Literal) any {
-	as.str.WriteString(fmt.Sprintf("%v", l.value))
-	return nil
-}
-
-func (as *ExprToRPN) visitGrouping(g *Grouping) any {
-	g.expression.accept(as)
-	as.str.WriteString(" group")
-	return nil
-}
-
-func (as *ExprToRPN) visitUnary(u *Unary) any {
-	u.right.accept(as)
-	as.str.WriteString(fmt.Sprintf(" %s", u.op.lexeme))
-	return nil
-}
-
-func (as *ExprToRPN) visitVariable(va *Variable) any {
-	as.str.WriteString(va.name.lexeme)
-	return nil
-}
-
-func (as *ExprToRPN) visitAssignment(a *Assign) any {
-	as.str.WriteString(fmt.Sprintf("%v %s =", a.value, a.variable.lexeme))
-	return nil
-}
-
-func (as *ExprToRPN) visitLogical(lo *Logical) any {
-	lo.left.accept(as)
-	lo.right.accept(as)
-	as.str.WriteString(" or")
-	return nil
-}

globals.go

@@ -0,0 +1,17 @@
+package main
+
+import "time"
+
+type ClockFun struct{}
+
+func (cf *ClockFun) call(i *Interpreter, args ...any) any {
+	return time.Now().Unix()
+}
+
+func (cf *ClockFun) arity() int {
+	return 0
+}
+
+func defineGlobals(env *Environment) {
+	env.define("clock", &ClockFun{})
+}

glox.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"fmt"
 	"log"
 	"os"
 )
@@ -27,12 +28,22 @@ func (gl *Glox) runPrompt() {
 	scanner := bufio.NewScanner(os.Stdin)
 	scanner.Split(bufio.ScanLines)
 
+	doRun := func(line []byte) {
+		defer func() {
+			if err := recover(); err != nil {
+				log.Println(err)
+			}
+		}()
+
+		gl.run(line)
+	}
+
 	for {
 		print("> ")
 		if !scanner.Scan() {
 			break
 		}
-		gl.run(scanner.Bytes())
+		doRun(scanner.Bytes())
 	}
 }
 
@@ -47,11 +58,29 @@ func (gl *Glox) runFile(path string) {
 }
 
 func (gl *Glox) run(source []byte) {
-	tokens, _ := newScanner(source).scan()
+	tokens, err := newScanner(source).scan()
 
-	stmts, _ := newParser(tokens).parse()
+	if err != nil {
+		panic(err)
+	}
 
-	// fmt.Println(AstStringer{stmts: stmts})
+	stmts, parseErrs := newParser(tokens).parse()
 
-	gl.Interpreter.interpret(stmts)
+	if parseErrs != nil {
+		panic(parseErrs)
+	}
+
+	fmt.Println(AstStringer{stmts: stmts})
+
+	resolveErrs := newResolver(gl.Interpreter).resolveStmts(stmts...)
+
+	if resolveErrs != nil {
+		panic(resolveErrs)
+	}
+
+	interpreterErrs := gl.Interpreter.interpret(stmts)
+
+	if interpreterErrs != nil {
+		panic(interpreterErrs)
+	}
 }

interpreter.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"reflect"
@@ -8,8 +9,11 @@ import (
 )
 
 type Interpreter struct {
-	env    *Environment
-	errors []error
+	env     *Environment
+	globals *Environment
+	locals  map[Expr]int
+	errors  []error
+	brk     bool
 }
 
 type RuntimeError struct {
@@ -17,15 +21,30 @@ type RuntimeError struct {
 	msg   string
 }
 
+type Return struct {
+	val any
+}
+
 func (re *RuntimeError) Error() string {
 	return fmt.Sprintf("RuntimeError [%d][%s] Error: %s", re.token.line, re.token.typ, re.msg)
 }
 
 func newInterpreter() *Interpreter {
-	return &Interpreter{env: newEnvironment(nil)}
+
+	globals := newEnvironment(nil)
+
+	defineGlobals(globals)
+
+	return &Interpreter{
+		env:     globals,
+		globals: globals,
+		locals:  map[Expr]int{},
+		errors:  []error{},
+		brk:     false,
+	}
 }
 
-func (i *Interpreter) interpret(stmts []Stmt) []error {
+func (i *Interpreter) interpret(stmts []Stmt) error {
 	defer i.recover()
 
 	i.errors = []error{}
@@ -34,7 +53,7 @@ func (i *Interpreter) interpret(stmts []Stmt) []error {
 		stmt.accept(i)
 	}
 
-	return i.errors
+	return errors.Join(i.errors...)
 }
 
 func (i *Interpreter) recover() {
@@ -119,25 +138,22 @@ func (i *Interpreter) visitUnary(u *Unary) any {
 }
 
 func (i *Interpreter) visitVariable(v *Variable) any {
-
-	if !i.env.exists(v.name.lexeme) {
-		i.panic(&RuntimeError{v.name, fmt.Sprintf("Can't assign: undefined variable '%s'.", v.name.lexeme)})
-	}
-
-	val := i.env.get(v.name.lexeme)
-	return val
+	return i.lookUpVariable(v.name, v)
 }
 
 func (i *Interpreter) visitAssignment(a *Assign) any {
+	val := i.evaluate(a.value)
+	distance, isLocal := i.locals[a]
 
-	if !i.env.exists(a.variable.lexeme) {
-		i.panic(&RuntimeError{a.variable, fmt.Sprintf("Can't assign: undefined variable '%s'.", a.variable.lexeme)})
+	if isLocal {
+		i.env.assignAt(distance, a.variable, val)
+		return val
 	}
 
-	val := i.evaluate(a.value)
-
-	i.env.set(a.variable.lexeme, val)
-
+	err := i.globals.assign(a.variable, val)
+	if err != nil {
+		i.panic(err)
+	}
 	return val
 }
 
@@ -155,6 +171,60 @@ func (i *Interpreter) visitLogical(lo *Logical) any {
 	return i.evaluate(lo.right)
 }
 
+func (i *Interpreter) visitCall(c *Call) any {
+
+	callee := i.evaluate(c.callee)
+
+	args := []any{}
+
+	for _, arg := range c.args {
+		args = append(args, i.evaluate(arg))
+	}
+
+	callable, ok := callee.(Callable)
+
+	if !ok {
+		i.panic(&RuntimeError{c.paren, "Can only call function and classes."})
+	}
+
+	if callable.arity() != len(args) {
+		i.panic(&RuntimeError{
+			c.paren,
+			fmt.Sprintf(
+				"Expected %d arguments  but got %d",
+				callable.arity(),
+				len(args),
+			),
+		})
+	}
+
+	return callable.call(i, args...)
+}
+
+func (i *Interpreter) visitFunStmt(f *FunStmt) {
+	i.env.define(f.name.lexeme, newFunction(f.name, f.args, f.body, i.env))
+}
+
+func (i *Interpreter) visitClassStmt(c *ClassStmt) {
+	i.env.define(c.name.lexeme, nil)
+	class := &Class{c.name.lexeme}
+	i.env.assign(c.name, class)
+
+}
+func (i *Interpreter) visitLambda(l *Lambda) any {
+	return newFunction(l.name, l.args, l.body, i.env)
+}
+
+func (i *Interpreter) visitReturnStmt(r *ReturnStmt) {
+	var value any
+
+	if r.value != nil {
+		value = i.evaluate(r.value)
+	}
+
+	panic(Return{value})
+}
+
 func (i *Interpreter) visitPrintStmt(p *PrintStmt) {
 	fmt.Printf("%v\n", i.evaluate(p.val))
 }
@@ -171,23 +241,41 @@ func (i *Interpreter) visitVarStmt(v *VarStmt) {
 		val = i.evaluate(v.initializer)
 	}
 
-	i.env.set(v.name.lexeme, val)
+	i.env.define(v.name.lexeme, val)
 }
 
 func (i *Interpreter) visitBlockStmt(b *BlockStmt) {
+	i.executeBlock(b.stmts, newEnvironment(i.env))
+}
+
+func (i *Interpreter) executeBlock(stmts []Stmt, current *Environment) {
 
 	parentEnv := i.env
-	i.env = newEnvironment(parentEnv)
+	i.env = current
+
+	// need to restore environment after
+	// panic(Return) in visitReturnStmt
+	defer func() {
+		i.env = parentEnv
+	}()
+
+	for _, stmt := range stmts {
+
+		if i.brk {
+			break
+		}
 
-	for _, stmt := range b.stmts {
 		stmt.accept(i)
 	}
 
-	i.env = parentEnv
+}
+
+func (i *Interpreter) visitBreakStmt(b *BreakStmt) {
+	i.brk = true
 }
 
 func (i *Interpreter) visitIfStmt(iff *IfStmt) {
-	if isTruthy(i.evaluate(iff.expr)) {
+	if isTruthy(i.evaluate(iff.cond)) {
 		iff.then.accept(i)
 
 	} else if iff.or != nil {
@@ -203,9 +291,11 @@ func (i *Interpreter) visitEnvStmt(e *EnvStmt) {
 
 	for walker != nil {
 		flatten = slices.Insert(flatten, 0, walker)
-		walker = walker.parent
+		walker = walker.enclosing
 	}
 
+	fmt.Printf("globals: %+v\n", *i.globals)
+
 	for ident, e := range flatten {
 		fmt.Printf("%*s", ident, "")
 		fmt.Printf("%+v\n", *e)
@@ -214,10 +304,30 @@ func (i *Interpreter) visitEnvStmt(e *EnvStmt) {
 
 func (i *Interpreter) visitWhileStmt(w *WhileStmt) {
 	for isTruthy(i.evaluate(w.cond)) {
+
+		if i.brk {
+			i.brk = false
+			break
+		}
+
 		w.body.accept(i)
 	}
 }
 
+func (i *Interpreter) resolve(expr Expr, depth int) {
+	i.locals[expr] = depth
+}
+
+func (i *Interpreter) lookUpVariable(name Token, expr Expr) any {
+	distance, isLocal := i.locals[expr]
+
+	if !isLocal {
+		return i.globals.get(name.lexeme)
+	}
+
+	return i.env.getAt(distance, name.lexeme)
+}
+
 func (i *Interpreter) panic(re *RuntimeError) {
 	i.errors = append(i.errors, re)
 	log.Println(re)

parser.go

@@ -1,8 +1,8 @@
 package main
 
 import (
+	"errors"
 	"fmt"
-	"log"
 )
 
 type Parser struct {
@@ -17,7 +17,12 @@ type ParseError struct {
 }
 
 func (pe *ParseError) Error() string {
-	return fmt.Sprintf("ParseError [%d][%s]: %s", pe.token.line, pe.token.typ, pe.message)
+	return fmt.Sprintf(
+		"ParseError [%d][%s]: %s",
+		pe.token.line,
+		pe.token.typ,
+		pe.message,
+	)
 }
 
 func newParser(tokens []Token) *Parser {
@@ -28,7 +33,7 @@ func newParser(tokens []Token) *Parser {
 }
 
 // program -> declaration* EOF
-func (p *Parser) parse() ([]Stmt, []error) {
+func (p *Parser) parse() ([]Stmt, error) {
 	defer p.recover()
 
 	stmts := []Stmt{}
@@ -40,21 +45,31 @@ func (p *Parser) parse() ([]Stmt, []error) {
 		}
 	}
 
-	return stmts, p.errors
+	return stmts, errors.Join(p.errors...)
 }
 
-// declaration -> varDecl | statement
+// declaration ->
+// varDecl | funDecl | classDecl | statement
 func (p *Parser) declaration() Stmt {
 	defer p.synchronize()
 	if p.match(VAR) {
 		return p.varDecl()
 	}
+
+	if p.match(FUN) {
+		return p.function("function")
+	}
+
+	if p.match(CLASS) {
+		return p.classDecl()
+	}
+
 	return p.statement()
 }
 
 // varDecl -> "var" IDENTIFIER ("=" expression)? ";"
 func (p *Parser) varDecl() Stmt {
-	name := p.consume(IDENTIFIER, "expect identifier for variable")
+	name := p.consume(IDENTIFIER, "Expect identifier for variable")
 
 	var initializer Expr = nil
 	if p.match(EQUAL) {
@@ -66,12 +81,59 @@ func (p *Parser) varDecl() Stmt {
 	return &VarStmt{name, initializer}
 }
 
+// classDecl -> "class" IDENTIFIER "{" function* "}"
+func (p *Parser) classDecl() Stmt {
+	name := p.consume(IDENTIFIER, "Expect identifier for variable")
+	p.consume(LEFT_BRACE, "Expect '{' after class identifier")
+
+	methods := []FunStmt{}
+	for !p.isAtEnd() && !p.check(RIGHT_BRACE) {
+		methods = append(methods, *p.function("method"))
+	}
+	p.consume(RIGHT_BRACE, "Expect '}' after class definition")
+	return &ClassStmt{name, methods}
+}
+
+// funDecl -> "fun" function
+// function -> IDENTIFIER "("  parameters? ")" blockStmt
+// parameters -> IDENTIFIER ( "," IDENTIFIER )*
+func (p *Parser) function(kind string) *FunStmt {
+	name := p.consume(IDENTIFIER, fmt.Sprintf("Expect %s name.", kind))
+
+	p.consume(LEFT_PAREN, fmt.Sprintf("Expect '(' after %s name.", kind))
+
+	args := []Token{}
+	for !p.check(RIGHT_PAREN) {
+		args = append(
+			args,
+			p.consume(
+				IDENTIFIER,
+				fmt.Sprintf("Expect %s argument.", kind),
+			),
+		)
+
+		if p.check(COMMA) {
+			p.advance()
+		}
+	}
+
+	p.consume(RIGHT_PAREN, fmt.Sprintf("Expect ')' after %s name.", kind))
+	p.consume(LEFT_BRACE, fmt.Sprintf("Expect '{' after %s arguments.", kind))
+
+	body := p.block()
+
+	return &FunStmt{name, args, body}
+}
+
 // statement ->  exprStmt
 //
 //	| whileStmt
+//	| forStmt
 //	| printStmt
 //	| blockStmt
+//	| breakStmt
 //	| ifStmt
+//	| returnStmt
 //	| env
 func (p *Parser) statement() Stmt {
 	if p.match(PRINT) {
@@ -94,6 +156,18 @@ func (p *Parser) statement() Stmt {
 		return p.whileStmt()
 	}
 
+	if p.match(FOR) {
+		return p.forStmt()
+	}
+
+	if p.match(BREAK) {
+		return p.breakStmt()
+	}
+
+	if p.match(RETURN) {
+		return p.returnStmt()
+	}
+
 	return p.exprStmt()
 }
 
@@ -121,8 +195,7 @@ func (p *Parser) printStmt() Stmt {
 	return &PrintStmt{expr}
 }
 
-// blockStmt -> "{" statement* "}"
-func (p *Parser) blockStmt() Stmt {
+func (p *Parser) block() []Stmt {
 
 	stmts := []Stmt{}
 	for !p.check(RIGHT_BRACE) && !p.isAtEnd() {
@@ -131,7 +204,18 @@ func (p *Parser) blockStmt() Stmt {
 
 	p.consume(RIGHT_BRACE, "Unclosed block: Expected '}'.")
 
-	return &BlockStmt{stmts}
+	return stmts
+}
+
+// blockStmt -> "{" statement* "}"
+func (p *Parser) blockStmt() *BlockStmt {
+	return &BlockStmt{p.block()}
+}
+
+// breakStmt -> break ";"
+func (p *Parser) breakStmt() Stmt {
+	p.consume(SEMICOLON, "Expect ';' after break.")
+	return &BreakStmt{}
 }
 
 // if -> "if" "(" expression ")" statement ("else" statement)?
@@ -160,12 +244,73 @@ func (p *Parser) whileStmt() Stmt {
 	return &WhileStmt{cond, body}
 }
 
+// for -> "for" ( "(" ( varDecl | exprStmt | ";" ) expression? ";" expression  ")" )? statement
+func (p *Parser) forStmt() Stmt {
+
+	if p.check(LEFT_BRACE) {
+		return &WhileStmt{&Literal{true}, p.statement()}
+	}
+
+	p.consume(LEFT_PAREN, "Expect '(' after 'for'.")
+
+	var init Stmt
+
+	if p.match(SEMICOLON) {
+		init = nil
+	} else if p.match(VAR) {
+		init = p.varDecl()
+	} else {
+		init = p.exprStmt()
+	}
+
+	var cond Expr
+
+	if !p.check(SEMICOLON) {
+		cond = p.expression()
+	}
+
+	p.consume(SEMICOLON, "Expect ';' after for loop condition;")
+
+	var incr Expr
+
+	if !p.check(RIGHT_PAREN) {
+		incr = p.expression()
+	}
+
+	p.consume(RIGHT_PAREN, "Expect ')' after for clauses;")
+
+	var body = p.statement()
+
+	if incr != nil {
+		body = &BlockStmt{[]Stmt{body, &ExprStmt{incr}}}
+	}
+
+	if cond == nil {
+		cond = &Literal{true}
+	}
+
+	body = &WhileStmt{cond, body}
+
+	if init != nil {
+		body = &BlockStmt{[]Stmt{init, body}}
+	}
+
+	return body
+}
+
 // env -> "env" ";"
 func (p *Parser) envStmt() Stmt {
 	p.consume(SEMICOLON, "Expect ';' after 'env'.")
 	return &EnvStmt{}
 }
 
+// return -> "return" expression ";"
+func (p *Parser) returnStmt() Stmt {
+	ret := p.expression()
+	p.consume(SEMICOLON, "Expect ';' after return;")
+	return &ReturnStmt{ret}
+}
+
 // expression -> assignment
 func (p *Parser) expression() Expr {
 	return p.assignment()
@@ -276,10 +421,52 @@ func (p *Parser) unary() Expr {
 		return &Unary{op, right}
 	}
 
-	return p.primary()
+	return p.call()
 }
 
-// primary -> NUMBER | STRING | "true" | "false" | "nil" | "(" expression ")" | IDENTIFIER
+// call ->  primary ( "(" arguments? ")"  )*
+func (p *Parser) call() Expr {
+	expr := p.primary()
+
+	for {
+		if p.match(LEFT_PAREN) {
+			expr = p.arguments(expr)
+		} else {
+			break
+		}
+	}
+
+	return expr
+}
+
+// arguments ->  expression ( "," expression )*
+func (p *Parser) arguments(callee Expr) Expr {
+	arguments := []Expr{}
+
+	if !p.check(RIGHT_PAREN) {
+		for {
+			arguments = append(arguments, p.expression())
+
+			if !p.match(COMMA) {
+				break
+			}
+		}
+	}
+
+	paren := p.consume(RIGHT_PAREN, "Expect ')' after arguments.")
+
+	return &Call{callee, paren, arguments}
+}
+
+// primary -> IDENTIFIER
+//
+//	| NUMBER
+//	| STRING
+//	| "true"
+//	| "false"
+//	| "nil"
+//	| "(" expression ")"
+//	| lambda
 func (p *Parser) primary() Expr {
 	switch {
 	case p.match(FALSE):
@@ -290,6 +477,10 @@ func (p *Parser) primary() Expr {
 		return &Literal{nil}
 	}
 
+	if p.match(FUN) {
+		return p.lambda()
+	}
+
 	if p.match(NUMBER, STRING) {
 		return &Literal{p.previous().literal}
 	}
@@ -304,11 +495,39 @@ func (p *Parser) primary() Expr {
 		return &Grouping{expr}
 	}
 
-	// p.panic(&ParseError{p.peek(), "Expect expression"})
+	p.panic(&ParseError{p.peek(), "Expect expression"})
 
 	return nil
 }
 
+func (p *Parser) lambda() Expr {
+	name := p.previous()
+
+	p.consume(LEFT_PAREN, "Expect '(' before lambda arguments.")
+
+	args := []Token{}
+	for !p.check(RIGHT_PAREN) {
+		args = append(
+			args,
+			p.consume(
+				IDENTIFIER,
+				"Expect lambda argument.",
+			),
+		)
+
+		if p.check(COMMA) {
+			p.advance()
+		}
+	}
+
+	p.consume(RIGHT_PAREN, "Expect ')' after lambda arguments.")
+	p.consume(LEFT_BRACE, "Expect '{' before lambda body.")
+
+	body := p.block()
+
+	return &Lambda{name, args, body}
+}
+
 func (p *Parser) previous() Token {
 	return p.tokens[p.current-1]
 }
@@ -391,7 +610,6 @@ func (p *Parser) recover() {
 
 func (p *Parser) panic(pe *ParseError) {
 	p.errors = append(p.errors, pe)
-	log.Println(pe)
 	panic(pe)
 }
 

resolver.go

@@ -0,0 +1,193 @@
+package main
+
+type Scope map[string]bool
+
+type Resolver struct {
+	interpreter *Interpreter
+	scopes      Stack[Scope]
+}
+
+type ResolveError struct {
+	msg string
+}
+
+func (r *ResolveError) Error() string {
+	return r.msg
+}
+
+func newResolver(i *Interpreter) *Resolver {
+	return &Resolver{i, NewStack[Scope]()}
+}
+
+func (r *Resolver) resolveStmts(stmts ...Stmt) error {
+	for _, stmt := range stmts {
+		stmt.accept(r)
+	}
+
+	return nil
+}
+
+func (r *Resolver) resolveExprs(exprs ...Expr) error {
+	for _, expr := range exprs {
+		expr.accept(r)
+	}
+
+	return nil
+}
+
+func (r *Resolver) beginScope() {
+	r.scopes.Push(map[string]bool{})
+}
+
+func (r *Resolver) endScope() {
+	r.scopes.Pop()
+}
+
+func (r *Resolver) declare(token Token) {
+	if !r.scopes.Empty() {
+		r.scopes.Peek()[token.lexeme] = false
+	}
+}
+
+func (r *Resolver) define(token Token) {
+	if !r.scopes.Empty() {
+		r.scopes.Peek()[token.lexeme] = true
+	}
+}
+
+func (r *Resolver) visitBlockStmt(b *BlockStmt) {
+	r.beginScope()
+	r.resolveStmts(b.stmts...)
+	r.endScope()
+}
+
+func (r *Resolver) visitVarStmt(v *VarStmt) {
+	r.declare(v.name)
+	if v.initializer != nil {
+		r.resolveExprs(v.initializer)
+	}
+	r.define(v.name)
+}
+
+func (r *Resolver) visitVariable(v *Variable) any {
+	if !r.scopes.Empty() {
+		defined, declared := r.scopes.Peek()[v.name.lexeme]
+
+		if declared && !defined {
+			panic(&ResolveError{"Can't read local variable in its own initializer."})
+		}
+	}
+
+	r.resolveLocal(v, v.name)
+	return nil
+}
+
+func (r *Resolver) visitAssignment(a *Assign) any {
+	r.resolveExprs(a.value)
+	r.resolveLocal(a, a.variable)
+	return nil
+}
+
+func (r *Resolver) resolveLocal(expr Expr, name Token) {
+	for i := r.scopes.Size() - 1; i >= 0; i-- {
+		if _, exists := r.scopes.At(i)[name.lexeme]; exists {
+			r.interpreter.resolve(expr, r.scopes.Size()-1-i)
+			return
+		}
+	}
+}
+
+func (r *Resolver) visitFunStmt(fun *FunStmt) {
+	r.declare(fun.name)
+	r.define(fun.name)
+	r.resolveFun(fun)
+}
+
+func (r *Resolver) resolveFun(fun *FunStmt) {
+	r.beginScope()
+	for _, arg := range fun.args {
+		r.declare(arg)
+		r.define(arg)
+	}
+	r.resolveStmts(fun.body...)
+	r.endScope()
+}
+
+func (r *Resolver) visitExprStmt(es *ExprStmt) {
+	r.resolveExprs(es.expr)
+}
+
+func (r *Resolver) visitBreakStmt(b *BreakStmt) {}
+func (r *Resolver) visitEnvStmt(b *EnvStmt)     {}
+func (r *Resolver) visitIfStmt(ifs *IfStmt) {
+	r.resolveExprs(ifs.cond)
+	r.resolveStmts(ifs.then)
+	if ifs.or != nil {
+		r.resolveStmts(ifs.or)
+	}
+}
+
+func (r *Resolver) visitPrintStmt(p *PrintStmt) {
+	r.resolveExprs(p.val)
+}
+
+func (r *Resolver) visitReturnStmt(ret *ReturnStmt) {
+	if ret.value != nil {
+		r.resolveExprs(ret.value)
+	}
+}
+
+func (r *Resolver) visitWhileStmt(w *WhileStmt) {
+	r.resolveExprs(w.cond)
+	r.resolveStmts(w.body)
+}
+
+func (r *Resolver) visitBinary(b *Binary) any {
+	r.resolveExprs(b.left)
+	r.resolveExprs(b.right)
+	return nil
+}
+
+func (r *Resolver) visitCall(c *Call) any {
+	r.resolveExprs(c.callee)
+	for _, arg := range c.args {
+		r.resolveExprs(arg)
+	}
+	return nil
+}
+
+func (r *Resolver) visitGrouping(g *Grouping) any {
+	r.resolveExprs(g.expression)
+	return nil
+}
+
+func (r *Resolver) visitLambda(l *Lambda) any {
+	r.beginScope()
+	for _, arg := range l.args {
+		r.declare(arg)
+		r.define(arg)
+	}
+	r.resolveStmts(l.body...)
+	r.endScope()
+	return nil
+}
+
+func (r *Resolver) visitLiteral(l *Literal) any {
+	return nil
+}
+
+func (r *Resolver) visitLogical(l *Logical) any {
+	r.resolveExprs(l.left)
+	r.resolveExprs(l.right)
+	return nil
+}
+
+func (r *Resolver) visitUnary(u *Unary) any {
+	r.resolveExprs(u.right)
+	return nil
+}
+
+func (r *Resolver) visitClassStmt(c *ClassStmt) {
+	r.declare(c.name)
+	r.define(c.name)
+}

scanner.go

@@ -43,6 +43,7 @@ const (
 
 	// keywords
 	AND
+	BREAK
 	CLASS
 	ENV
 	ELSE
@@ -65,6 +66,7 @@ const (
 
 var keywords = map[string]TokenType{
 	"and":    AND,
+	"break":  BREAK,
 	"class":  CLASS,
 	"else":   ELSE,
 	"false":  FALSE,

stack.go

@@ -0,0 +1,47 @@
+package main
+
+type Stack[Item any] interface {
+	Push(Item)
+	Pop() Item
+	Peek() Item
+	At(int) Item
+	Size() int
+	Empty() bool
+}
+
+type node[Item any] struct {
+	item Item
+	next *node[Item]
+}
+
+type stack[OfType any] []OfType
+
+func NewStack[OfType any]() Stack[OfType] {
+	return &stack[OfType]{}
+}
+
+func (s *stack[Item]) Push(item Item) {
+	*s = append(*s, item)
+}
+
+func (s *stack[Item]) Pop() Item {
+	last := s.Peek()
+	*s = (*s)[:len(*s)-1]
+	return last
+}
+
+func (s *stack[Item]) At(idx int) Item {
+	return (*s)[idx]
+}
+
+func (s *stack[Item]) Peek() Item {
+	return (*s)[len(*s)-1]
+}
+
+func (s *stack[_]) Size() int {
+	return len(*s)
+}
+
+func (s *stack[_]) Empty() bool {
+	return s.Size() == 0
+}

stmt.go

@@ -3,11 +3,15 @@ package main
 type StmtVisitor interface {
 	visitIfStmt(i *IfStmt)
 	visitVarStmt(v *VarStmt)
+	visitEnvStmt(e *EnvStmt)
+	visitFunStmt(f *FunStmt)
 	visitExprStmt(es *ExprStmt)
 	visitPrintStmt(p *PrintStmt)
 	visitBlockStmt(b *BlockStmt)
-	visitEnvStmt(e *EnvStmt)
 	visitWhileStmt(w *WhileStmt)
+	visitBreakStmt(b *BreakStmt)
+	visitReturnStmt(r *ReturnStmt)
+	visitClassStmt(c *ClassStmt)
 }
 
 type Stmt interface {
@@ -36,7 +40,7 @@ type EnvStmt struct{}
 
 type IfStmt struct {
 	name Token
-	expr Expr
+	cond Expr
 	then Stmt
 	or   Stmt
 }
@@ -46,13 +50,34 @@ type WhileStmt struct {
 	body Stmt
 }
 
-func (i *IfStmt) stmt()    {}
-func (e *EnvStmt) stmt()   {}
-func (vs *VarStmt) stmt()  {}
-func (es *ExprStmt) stmt() {}
-func (p *PrintStmt) stmt() {}
-func (b *BlockStmt) stmt() {}
-func (w *WhileStmt) stmt() {}
+type ClassStmt struct {
+	name    Token
+	methods []FunStmt
+}
+
+type BreakStmt struct{}
+
+type FunStmt struct {
+	name Token
+	args []Token
+	body []Stmt
+}
+
+type ReturnStmt struct {
+	value Expr
+}
+
+func (i *IfStmt) stmt()     {}
+func (f *FunStmt) stmt()    {}
+func (e *EnvStmt) stmt()    {}
+func (vs *VarStmt) stmt()   {}
+func (es *ExprStmt) stmt()  {}
+func (p *PrintStmt) stmt()  {}
+func (b *BlockStmt) stmt()  {}
+func (w *WhileStmt) stmt()  {}
+func (b *BreakStmt) stmt()  {}
+func (r *ReturnStmt) stmt() {}
+func (c *ClassStmt) stmt()  {}
 
 func (p *PrintStmt) accept(v StmtVisitor) {
 	v.visitPrintStmt(p)
@@ -81,3 +106,19 @@ func (e *EnvStmt) accept(v StmtVisitor) {
 func (w *WhileStmt) accept(v StmtVisitor) {
 	v.visitWhileStmt(w)
 }
+
+func (b *BreakStmt) accept(v StmtVisitor) {
+	v.visitBreakStmt(b)
+}
+
+func (f *FunStmt) accept(v StmtVisitor) {
+	v.visitFunStmt(f)
+}
+
+func (r *ReturnStmt) accept(v StmtVisitor) {
+	v.visitReturnStmt(r)
+}
+
+func (c *ClassStmt) accept(v StmtVisitor) {
+	v.visitClassStmt(c)
+}

tests/for.lox

@@ -0,0 +1,36 @@
+
+print "full form -------------------------";
+for (var i = 0; i < 100; i = i + 20) print i;
+
+print "without init ----------------------";
+var n = 100;
+for (;n > 0; n = n - 20) print n;
+
+print "only cond -----------------------";
+
+var i = 1;
+for (;i < 100;) {
+    print i;
+    i = i + 10;
+}
+
+print "inf ---------------------------";
+
+var b = 0;
+for {
+    print b;
+    b = b + 5;
+    if (b > 10) break;
+
+    print "after break";
+}
+
+print "fibonachi ------------------------";
+var temp;
+var first = 0;
+
+for (var second = 1; first < 10000; second = temp + second) {
+    print first;
+    temp  = first;
+    first = second;
+}

tests/functions.lox

@@ -0,0 +1,71 @@
+
+print "native function";
+
+print clock();
+
+fun count(n) {
+    print n;
+    if (n > 1) count(n - 1);
+    print n;
+}
+
+count(10);
+
+fun hi(name, surname) {
+    print "hello, " + name + " " + surname + "!";
+}
+
+hi("John", "Doe");
+
+
+fun re(turn) {
+    print "before return";
+    return turn;
+    print "should not be printed";
+}
+
+print re("turn");
+
+
+fun sum(start, end) {
+    if (start == end) return start;
+    return start + sum(start + 1, end);
+}
+
+print sum(1, 3);
+
+fun fib(n) {
+    if (n <= 1) return n;
+
+    return fib(n - 2) + fib(n - 1);
+}
+
+for (var i = 1; i <= 10; i = i + 1) {
+    print fib(i);
+}
+
+fun makeCounter() {
+    var i = 0;
+
+    fun incr() {
+        i = i + 1;
+        print i;
+    }
+
+    return incr;
+}
+
+var counter = makeCounter();
+
+counter();
+counter();
+
+fun thrice(fn) {
+    for (var i = 1; i <= 3; i = i + 1) {
+        fn(i);
+    }
+}
+
+thrice(fun (a) { print a; });
+
+print fun () { return "hello, "; }() + "world";

tests/scope_and_binding.lox

@@ -0,0 +1,12 @@
+var a = "global";
+
+{
+    fun showA() {
+        print a;
+    }
+
+    showA();
+    var a = "inner v2";
+
+    showA();
+}

tests/while.lox

@@ -0,0 +1,35 @@
+var iterator = 100;
+
+{
+    while (iterator > 0) {
+       {
+         print iterator;
+        iterator = iterator - 2;
+       }
+    }
+}
+
+
+{
+    while (iterator < 100) {
+        {
+            {
+                print iterator;
+                iterator = iterator + 2;
+
+                if (iterator > 50) break;
+
+                print "shoud not be printed after 50";
+            }
+
+            print "OUTER also shoud not be printed after 50";
+
+        }
+    }
+}
+
+while (iterator < 100) iterator = iterator + 2; 
+
+
+
+print iterator;

tokentype_string.go

@@ -31,28 +31,29 @@ func _() {
 	_ = x[STRING-20]
 	_ = x[NUMBER-21]
 	_ = x[AND-22]
-	_ = x[CLASS-23]
-	_ = x[ENV-24]
-	_ = x[ELSE-25]
-	_ = x[FALSE-26]
-	_ = x[FUN-27]
-	_ = x[FOR-28]
-	_ = x[IF-29]
-	_ = x[NIL-30]
-	_ = x[OR-31]
-	_ = x[PRINT-32]
-	_ = x[RETURN-33]
-	_ = x[SUPER-34]
-	_ = x[THIS-35]
-	_ = x[TRUE-36]
-	_ = x[VAR-37]
-	_ = x[WHILE-38]
-	_ = x[EOF-39]
+	_ = x[BREAK-23]
+	_ = x[CLASS-24]
+	_ = x[ENV-25]
+	_ = x[ELSE-26]
+	_ = x[FALSE-27]
+	_ = x[FUN-28]
+	_ = x[FOR-29]
+	_ = x[IF-30]
+	_ = x[NIL-31]
+	_ = x[OR-32]
+	_ = x[PRINT-33]
+	_ = x[RETURN-34]
+	_ = x[SUPER-35]
+	_ = x[THIS-36]
+	_ = x[TRUE-37]
+	_ = x[VAR-38]
+	_ = x[WHILE-39]
+	_ = x[EOF-40]
 }
 
-const _TokenType_name = "LEFT_PARENRIGHT_PARENLEFT_BRACERIGHT_BRACECOMMADOTMINUSPLUSSEMICOLONSLASHSTARBANGBANG_EQUALEQUALEQUAL_EQUALGREATERGREATER_EQUALLESSLESS_EQUALIDENTIFIERSTRINGNUMBERANDCLASSENVELSEFALSEFUNFORIFNILORPRINTRETURNSUPERTHISTRUEVARWHILEEOF"
+const _TokenType_name = "LEFT_PARENRIGHT_PARENLEFT_BRACERIGHT_BRACECOMMADOTMINUSPLUSSEMICOLONSLASHSTARBANGBANG_EQUALEQUALEQUAL_EQUALGREATERGREATER_EQUALLESSLESS_EQUALIDENTIFIERSTRINGNUMBERANDBREAKCLASSENVELSEFALSEFUNFORIFNILORPRINTRETURNSUPERTHISTRUEVARWHILEEOF"
 
-var _TokenType_index = [...]uint8{0, 10, 21, 31, 42, 47, 50, 55, 59, 68, 73, 77, 81, 91, 96, 107, 114, 127, 131, 141, 151, 157, 163, 166, 171, 174, 178, 183, 186, 189, 191, 194, 196, 201, 207, 212, 216, 220, 223, 228, 231}
+var _TokenType_index = [...]uint8{0, 10, 21, 31, 42, 47, 50, 55, 59, 68, 73, 77, 81, 91, 96, 107, 114, 127, 131, 141, 151, 157, 163, 166, 171, 176, 179, 183, 188, 191, 194, 196, 199, 201, 206, 212, 217, 221, 225, 228, 233, 236}
 
 func (i TokenType) String() string {
 	if i < 0 || i >= TokenType(len(_TokenType_index)-1) {