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How to use Lex method of parser Package

Best Syzkaller code snippet using parser.Lex

ast.go

Source:ast.go

1package expr2import (3	"bytes"4	"fmt"5	"strconv"6	"strings"7	"text/scanner"8	"unicode"9)10const (11	TokenEOF = -(iota + 1)12	TokenIdent13	TokenInt14	TokenFloat15	TokenOperator16)17type lexer struct {18	scan  scanner.Scanner19	token rune20	text  string21}22func (lex *lexer) getToken() rune {23	return lex.token24}25func (lex *lexer) getText() string {26	return lex.text27}28func (lex *lexer) next() {29	token := lex.scan.Scan()30	text := lex.scan.TokenText()31	switch token {32	case scanner.EOF:33		lex.token = TokenEOF34		lex.text = text35	case scanner.Ident:36		lex.token = TokenIdent37		lex.text = text38	case scanner.Int:39		lex.token = TokenInt40		lex.text = text41	case scanner.Float:42		lex.token = TokenFloat43		lex.text = text44	case '+', '-', '*', '/', '%', '~':45		lex.token = TokenOperator46		lex.text = text47	case '&', '|', '=':48		var buffer bytes.Buffer49		lex.token = TokenOperator50		buffer.WriteRune(token)51		next := lex.scan.Peek()52		if next == token {53			buffer.WriteRune(next)54			lex.scan.Scan()55		}56		lex.text = buffer.String()57	case '>', '<', '!':58		var buffer bytes.Buffer59		lex.token = TokenOperator60		buffer.WriteRune(token)61		next := lex.scan.Peek()62		if next == '=' {63			buffer.WriteRune(next)64			lex.scan.Scan()65		}66		lex.text = buffer.String()67	default:68		if token >= 0 {69			lex.token = token70			lex.text = text71		} else {72			msg := fmt.Sprintf("got unknown token:%q, text:%s", lex.token, lex.text)73			panic(lexPanic(msg))74		}75	}76	//fmt.Printf("token:%d, text:%s\n", lex.token, lex.text)77}78type lexPanic string79// describe returns a string describing the current token, for use in errors.80func (lex *lexer) describe() string {81	switch lex.token {82	case TokenEOF:83		return "end of file"84	case TokenIdent:85		return fmt.Sprintf("identifier %s", lex.getText())86	case TokenInt, TokenFloat:87		return fmt.Sprintf("number %s", lex.getText())88	}89	return fmt.Sprintf("%q", rune(lex.getToken())) // any other rune90}91func precedence(token rune, text string) int {92	if token == TokenOperator {93		switch text {94		case "~", "!":95			return 996		case "*", "/", "%":97			return 898		case "+", "-":99			return 7100		case ">", ">=", "<", "<=":101			return 6102		case "!=", "==", "=":103			return 5104		case "&":105			return 4106		case "|":107			return 3108		case "&&":109			return 2110		case "||":111			return 1112		default:113			msg := fmt.Sprintf("unknown operator:%s", text)114			panic(lexPanic(msg))115		}116	}117	return 0118}119// ---- parser ----120type ExpressionParser struct {121	expression Expr122	variable   map[string]struct{}123}124func NewExpressionParser() *ExpressionParser {125	return &ExpressionParser{126		expression: nil,127		variable:   make(map[string]struct{}),128	}129}130// Parse parses the input string as an arithmetic expression.131//132//   expr = num                         a literal number, e.g., 3.14159133//        | id                          a variable name, e.g., x134//        | id '(' expr ',' ... ')'     a function call135//        | '-' expr                    a unary operator ( + - ! )136//        | expr '+' expr               a binary operator ( + - * / && & || | == )137//138func (parser *ExpressionParser) Parse(input string) (err error) {139	defer func() {140		switch x := recover().(type) {141		case nil:142			// no panic143		case lexPanic:144			err = fmt.Errorf("%s", x)145		default:146			// unexpected panic: resume state of panic.147			panic(x)148		}149	}()150	lex := new(lexer)151	lex.scan.Init(strings.NewReader(input))152	lex.scan.Mode = scanner.ScanIdents | scanner.ScanInts | scanner.ScanFloats153	lex.scan.IsIdentRune = parser.isIdentRune154	lex.next() // initial lookahead155	parser.expression = nil156	parser.variable = make(map[string]struct{})157	e := parser.parseExpr(lex)158	if lex.token != scanner.EOF {159		return fmt.Errorf("unexpected %s", lex.describe())160	}161	parser.expression = e162	return nil163}164func (parser *ExpressionParser) GetExpr() Expr {165	return parser.expression166}167func (parser *ExpressionParser) GetVariable() []string {168	variable := make([]string, 0, len(parser.variable))169	for v := range parser.variable {170		if v != "true" && v != "false" {171			variable = append(variable, v)172		}173	}174	return variable175}176func (parser *ExpressionParser) isIdentRune(ch rune, i int) bool {177	return ch == '$' || ch == '_' || unicode.IsLetter(ch) || unicode.IsDigit(ch) && i > 0178}179func (parser *ExpressionParser) parseExpr(lex *lexer) Expr {180	return parser.parseBinary(lex, 1)181}182// binary = unary ('+' binary)*183// parseBinary stops when it encounters an184// operator of lower precedence than prec1.185func (parser *ExpressionParser) parseBinary(lex *lexer, prec1 int) Expr {186	lhs := parser.parseUnary(lex)187	for prec := precedence(lex.getToken(), lex.getText()); prec >= prec1; prec-- {188		for precedence(lex.getToken(), lex.getText()) == prec {189			op := lex.getText()190			lex.next() // consume operator191			rhs := parser.parseBinary(lex, prec+1)192			lhs = binary{op, lhs, rhs}193		}194	}195	return lhs196}197// unary = '+' expr | primary198func (parser *ExpressionParser) parseUnary(lex *lexer) Expr {199	if lex.getToken() == TokenOperator {200		op := lex.getText()201		if op == "+" || op == "-" || op == "~" || op == "!" {202			lex.next()203			return unary{op, parser.parseUnary(lex)}204		} else {205			msg := fmt.Sprintf("unary got unknown operator:%s", lex.getText())206			panic(lexPanic(msg))207		}208	}209	return parser.parsePrimary(lex)210}211// primary = id212//         | id '(' expr ',' ... ',' expr ')'213//         | num214//         | '(' expr ')'215func (parser *ExpressionParser) parsePrimary(lex *lexer) Expr {216	switch lex.token {217	case TokenIdent:218		id := lex.getText()219		lex.next()220		if lex.token != '(' {221			parser.variable[id] = struct{}{}222			return Var(id)223		}224		lex.next() // consume '('225		var args []Expr226		if lex.token != ')' {227			for {228				args = append(args, parser.parseExpr(lex))229				if lex.token != ',' {230					break231				}232				lex.next() // consume ','233			}234			if lex.token != ')' {235				msg := fmt.Sprintf("got %q, want ')'", lex.token)236				panic(lexPanic(msg))237			}238		}239		lex.next() // consume ')'240		return call{id, args}241	case TokenFloat:242		f, err := strconv.ParseFloat(lex.getText(), 64)243		if err != nil {244			panic(lexPanic(err.Error()))245		}246		lex.next() // consume number247		return literal{value: f}248	case TokenInt:249		i, err := strconv.ParseInt(lex.getText(), 10, 64)250		if err != nil {251			panic(lexPanic(err.Error()))252		}253		lex.next() // consume number254		return literal{value: i}255	case '(':256		lex.next() // consume '('257		e := parser.parseExpr(lex)258		if lex.token != ')' {259			msg := fmt.Sprintf("got %s, want ')'", lex.describe())260			panic(lexPanic(msg))261		}262		lex.next() // consume ')'263		return e264	}265	msg := fmt.Sprintf("unexpected %s", lex.describe())266	panic(lexPanic(msg))267}...

Lex

Using AI Code Generation

1import (2func main() {3	if len(args) != 1 {4		fmt.Println("Usage: go run 2.go <filename>")5	}6	p := lex.NewParser(filename)7	p.Lex()8}

Lex

Using AI Code Generation

1import (2var (3	terminals    = []string{"+", "-", "*", "/", "(", ")", "^", "sin", "cos", "tan", "sqrt", "log", "ln", "e", "pi", "x"}4	nonTerminals = []string{"S", "E", "F", "T", "G", "H", "A", "B", "C", "D", "R", "P", "Q", "U", "V", "W", "X", "Y", "Z"}5func main() {6	parser := Parser{}7	parser.Lex()8}9type Parser struct {10}11func (p *Parser) Lex() {12	p.stack = stack.New()13	p.resultStack = stack.New()14	p.tokenStack = stack.New()15	p.Read()16}17func (p *Parser) Read() {18	ui, err := tui.New(tui.NewHBox(19		tui.NewLabel("Enter the expression: "),20		tui.NewEntry(),21	if err != nil {22		log.Fatal(err)23	}24	entry := ui.Find("entry").(*tui.Entry)25	entry.OnSubmit(func(e *tui.Entry) {26		s := e.Text()27		p.Parse(s)28	})29	ui.SetKeybinding("Esc", func() { ui.Quit() })30	if err := ui.Run(); err != nil {31		log.Fatal(err)32	}33}34func (p *Parser) Parse

Lex

Using AI Code Generation

1import (2func main() {3	if len(os.Args) != 2 {4		fmt.Println("Usage: ./2 <input string>")5		os.Exit(1)6	}7	p := parser.NewParser(os.Args[1])8	for {9		tok := p.Lex()10		fmt.Println(tok)11		if tok == parser.EOF {12		}13	}14}

Lex

Using AI Code Generation

1import (2var (3const (4const (5var toknames = []string{6}7var opnames = []string{8}9var errors = []string{10}11const (

Lex

Using AI Code Generation

1import (2func main() {3	fmt.Println("Enter the input string")4	reader := bufio.NewReader(os.Stdin)5	input, _ := reader.ReadString('\n')6	parser.Lex(input)7}

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