Namespace packages with "urubu/"

10 files changed, 0 insertions, 3470 deletions

diff --git a/driver/parser/conflict_test.go b/driver/parser/conflict_test.go
deleted file mode 100644
index 1a75483..0000000
--- a/driver/parser/conflict_test.go
+++ /dev/null
@@ -1,524 +0,0 @@
-package parser
-
-import (
-	"strings"
-	"testing"
-
-	"grammar"
-	"spec/grammar/parser"
-)
-
-func TestParserWithConflicts(t *testing.T) {
-	tests := []struct {
-		caption string
-		specSrc string
-		src     string
-		cst     *Node
-	}{
-		{
-			caption: "when a shift/reduce conflict occurred, we prioritize the shift action",
-			specSrc: `
-#name test;
-
-expr
-    : expr assign expr
-	| id
-	;
-
-id: "[A-Za-z0-9_]+";
-assign: '=';
-`,
-			src: `foo=bar=baz`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					termNode("id", "foo"),
-				),
-				termNode("assign", "="),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("id", "bar"),
-					),
-					termNode("assign", "="),
-					nonTermNode("expr",
-						termNode("id", "baz"),
-					),
-				),
-			),
-		},
-		{
-			caption: "when a reduce/reduce conflict occurred, we prioritize the production defined earlier in the grammar",
-			specSrc: `
-#name test;
-
-s
-    : a
-	| b
-	;
-a
-    : id
-	;
-b
-    : id
-	;
-
-id: "[A-Za-z0-9_]+";
-`,
-			src: `foo`,
-			cst: nonTermNode("s",
-				nonTermNode("a",
-					termNode("id", "foo"),
-				),
-			),
-		},
-		{
-			caption: "left associativities defined earlier in the grammar have higher precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #left mul
-    #left add
-);
-
-expr
-    : expr add expr
-    | expr mul expr
-	| id
-    ;
-
-id: "[A-Za-z0-9_]+";
-add: '+';
-mul: '*';
-`,
-			src: `a+b*c*d+e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("id", "a"),
-					),
-					termNode("add", "+"),
-					nonTermNode("expr",
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "b"),
-							),
-							termNode("mul", "*"),
-							nonTermNode("expr",
-								termNode("id", "c"),
-							),
-						),
-						termNode("mul", "*"),
-						nonTermNode("expr",
-							termNode("id", "d"),
-						),
-					),
-				),
-				termNode("add", "+"),
-				nonTermNode("expr",
-					termNode("id", "e"),
-				),
-			),
-		},
-		{
-			caption: "left associativities defined in the same line have the same precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #left add sub
-);
-
-expr
-    : expr add expr
-    | expr sub expr
-	| id
-    ;
-
-id: "[A-Za-z0-9_]+";
-add: '+';
-sub: '-';
-`,
-			src: `a-b+c+d-e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("expr",
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "a"),
-							),
-							termNode("sub", "-"),
-							nonTermNode("expr",
-								termNode("id", "b"),
-							),
-						),
-						termNode("add", "+"),
-						nonTermNode("expr",
-							termNode("id", "c"),
-						),
-					),
-					termNode("add", "+"),
-					nonTermNode("expr",
-						termNode("id", "d"),
-					),
-				),
-				termNode("sub", "-"),
-				nonTermNode("expr",
-					termNode("id", "e"),
-				),
-			),
-		},
-		{
-			caption: "right associativities defined earlier in the grammar have higher precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #right r1
-    #right r2
-);
-
-expr
-    : expr r2 expr
-    | expr r1 expr
-	| id
-    ;
-
-whitespaces #skip
-    : "[\u{0009}\u{0020}]+";
-r1
-    : 'r1';
-r2
-    : 'r2';
-id
-    : "[A-Za-z0-9_]+";
-`,
-			src: `a r2 b r1 c r1 d r2 e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					termNode("id", "a"),
-				),
-				termNode("r2", "r2"),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						nonTermNode("expr",
-							termNode("id", "b"),
-						),
-						termNode("r1", "r1"),
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "c"),
-							),
-							termNode("r1", "r1"),
-							nonTermNode("expr",
-								termNode("id", "d"),
-							),
-						),
-					),
-					termNode("r2", "r2"),
-					nonTermNode("expr",
-						termNode("id", "e"),
-					),
-				),
-			),
-		},
-		{
-			caption: "right associativities defined in the same line have the same precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #right r1 r2
-);
-
-expr
-    : expr r2 expr
-    | expr r1 expr
-	| id
-    ;
-
-whitespaces #skip
-    : "[\u{0009}\u{0020}]+";
-r1
-    : 'r1';
-r2
-    : 'r2';
-id
-    : "[A-Za-z0-9_]+";
-`,
-			src: `a r2 b r1 c r1 d r2 e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					termNode("id", "a"),
-				),
-				termNode("r2", "r2"),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("id", "b"),
-					),
-					termNode("r1", "r1"),
-					nonTermNode("expr",
-						nonTermNode("expr",
-							termNode("id", "c"),
-						),
-						termNode("r1", "r1"),
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "d"),
-							),
-							termNode("r2", "r2"),
-							nonTermNode("expr",
-								termNode("id", "e"),
-							),
-						),
-					),
-				),
-			),
-		},
-		{
-			caption: "terminal symbols with an #assign directive defined earlier in the grammar have higher precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #assign a1
-    #assign a2
-);
-
-expr
-    : expr a2 expr
-    | expr a1 expr
-	| id
-    ;
-
-whitespaces #skip
-    : "[\u{0009}\u{0020}]+";
-a1
-    : 'a1';
-a2
-    : 'a2';
-id
-    : "[A-Za-z0-9_]+";
-`,
-			src: `a a2 b a1 c a1 d a2 e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					termNode("id", "a"),
-				),
-				termNode("a2", "a2"),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						nonTermNode("expr",
-							termNode("id", "b"),
-						),
-						termNode("a1", "a1"),
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "c"),
-							),
-							termNode("a1", "a1"),
-							nonTermNode("expr",
-								termNode("id", "d"),
-							),
-						),
-					),
-					termNode("a2", "a2"),
-					nonTermNode("expr",
-						termNode("id", "e"),
-					),
-				),
-			),
-		},
-		{
-			caption: "terminal symbols with an #assign directive defined in the same line have the same precedence",
-			specSrc: `
-#name test;
-
-#prec (
-    #assign a1 a2
-);
-
-expr
-    : expr a2 expr
-    | expr a1 expr
-	| id
-    ;
-
-whitespaces #skip
-    : "[\u{0009}\u{0020}]+";
-a1
-    : 'a1';
-a2
-    : 'a2';
-id
-    : "[A-Za-z0-9_]+";
-`,
-			src: `a a2 b a1 c a1 d a2 e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					termNode("id", "a"),
-				),
-				termNode("a2", "a2"),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("id", "b"),
-					),
-					termNode("a1", "a1"),
-					nonTermNode("expr",
-						nonTermNode("expr",
-							termNode("id", "c"),
-						),
-						termNode("a1", "a1"),
-						nonTermNode("expr",
-							nonTermNode("expr",
-								termNode("id", "d"),
-							),
-							termNode("a2", "a2"),
-							nonTermNode("expr",
-								termNode("id", "e"),
-							),
-						),
-					),
-				),
-			),
-		},
-		{
-			caption: "#left, #right, and #assign can be mixed",
-			specSrc: `
-#name test;
-
-#prec (
-    #left mul div
-    #left add sub
-    #assign else
-    #assign then
-    #right assign
-);
-
-expr
-    : expr add expr
-    | expr sub expr
-    | expr mul expr
-    | expr div expr
-    | expr assign expr
-    | if expr then expr
-    | if expr then expr else expr
-    | id
-    ;
-
-ws #skip: "[\u{0009}\u{0020}]+";
-if: 'if';
-then: 'then';
-else: 'else';
-id: "[A-Za-z0-9_]+";
-add: '+';
-sub: '-';
-mul: '*';
-div: '/';
-assign: '=';
-`,
-			src: `x = y = a + b * c - d / e + if f then if g then h else i`,
-			cst: nonTermNode(
-				"expr",
-				nonTermNode("expr",
-					termNode("id", "x"),
-				),
-				termNode("assign", "="),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("id", "y"),
-					),
-					termNode("assign", "="),
-					nonTermNode("expr",
-						nonTermNode("expr",
-							nonTermNode("expr",
-								nonTermNode("expr",
-									termNode("id", "a"),
-								),
-								termNode("add", "+"),
-								nonTermNode("expr",
-									nonTermNode("expr",
-										termNode("id", "b"),
-									),
-									termNode("mul", "*"),
-									nonTermNode("expr",
-										termNode("id", "c"),
-									),
-								),
-							),
-							termNode("sub", "-"),
-							nonTermNode("expr",
-								nonTermNode("expr",
-									termNode("id", "d"),
-								),
-								termNode("div", "/"),
-								nonTermNode("expr",
-									termNode("id", "e"),
-								),
-							),
-						),
-						termNode("add", "+"),
-						nonTermNode("expr",
-							termNode("if", "if"),
-							nonTermNode("expr",
-								termNode("id", "f"),
-							),
-							termNode("then", "then"),
-							nonTermNode("expr",
-								termNode("if", "if"),
-								nonTermNode("expr",
-									termNode("id", "g"),
-								),
-								termNode("then", "then"),
-								nonTermNode("expr",
-									termNode("id", "h"),
-								),
-								termNode("else", "else"),
-								nonTermNode("expr",
-									termNode("id", "i"),
-								),
-							),
-						),
-					),
-				),
-			),
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.caption, func(t *testing.T) {
-			ast, err := parser.Parse(strings.NewReader(tt.specSrc))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			b := grammar.GrammarBuilder{
-				AST: ast,
-			}
-			cg, _, err := b.Build()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			toks, err := NewTokenStream(cg, strings.NewReader(tt.src))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			gram := NewGrammar(cg)
-			tb := NewDefaultSyntaxTreeBuilder()
-			p, err := NewParser(toks, gram, SemanticAction(NewCSTActionSet(gram, tb)))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			err = p.Parse()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			if tt.cst != nil {
-				testTree(t, tb.Tree(), tt.cst)
-			}
-		})
-	}
-}
diff --git a/driver/parser/lac_test.go b/driver/parser/lac_test.go
deleted file mode 100644
index ed9a0b8..0000000
--- a/driver/parser/lac_test.go
+++ /dev/null
@@ -1,120 +0,0 @@
-package parser
-
-import (
-	"strings"
-	"testing"
-
-	"grammar"
-	"spec/grammar/parser"
-)
-
-func TestParserWithLAC(t *testing.T) {
-	specSrc := `
-#name test;
-
-s
-    : t t
-	;
-t
-    : c t
-	| d
-	;
-
-c: 'c';
-d: 'd';
-`
-
-	src := `ccd`
-
-	actLogWithLAC := []string{
-		"shift/c",
-		"shift/c",
-		"shift/d",
-		"miss",
-	}
-
-	actLogWithoutLAC := []string{
-		"shift/c",
-		"shift/c",
-		"shift/d",
-		"reduce/t",
-		"reduce/t",
-		"reduce/t",
-		"miss",
-	}
-
-	ast, err := parser.Parse(strings.NewReader(specSrc))
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	b := grammar.GrammarBuilder{
-		AST: ast,
-	}
-	gram, _, err := b.Build()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	t.Run("LAC is enabled", func(t *testing.T) {
-		semAct := &testSemAct{
-			gram: gram,
-		}
-
-		toks, err := NewTokenStream(gram, strings.NewReader(src))
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		p, err := NewParser(toks, NewGrammar(gram), SemanticAction(semAct))
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		err = p.Parse()
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		if len(semAct.actLog) != len(actLogWithLAC) {
-			t.Fatalf("unexpected action log; want: %+v, got: %+v", actLogWithLAC, semAct.actLog)
-		}
-
-		for i, e := range actLogWithLAC {
-			if semAct.actLog[i] != e {
-				t.Fatalf("unexpected action log; want: %+v, got: %+v", actLogWithLAC, semAct.actLog)
-			}
-		}
-	})
-
-	t.Run("LAC is disabled", func(t *testing.T) {
-		semAct := &testSemAct{
-			gram: gram,
-		}
-
-		toks, err := NewTokenStream(gram, strings.NewReader(src))
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		p, err := NewParser(toks, NewGrammar(gram), SemanticAction(semAct), DisableLAC())
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		err = p.Parse()
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		if len(semAct.actLog) != len(actLogWithoutLAC) {
-			t.Fatalf("unexpected action log; want: %+v, got: %+v", actLogWithoutLAC, semAct.actLog)
-		}
-
-		for i, e := range actLogWithoutLAC {
-			if semAct.actLog[i] != e {
-				t.Fatalf("unexpected action log; want: %+v, got: %+v", actLogWithoutLAC, semAct.actLog)
-			}
-		}
-	})
-}
diff --git a/driver/parser/parser.go b/driver/parser/parser.go
deleted file mode 100644
index 2eaa678..0000000
--- a/driver/parser/parser.go
+++ /dev/null
@@ -1,416 +0,0 @@
-package parser
-
-import (
-	"fmt"
-)
-
-type Grammar interface {
-	// InitialState returns the initial state of a parser.
-	InitialState() int
-
-	// StartProduction returns the start production of grammar.
-	StartProduction() int
-
-	// Action returns an ACTION entry corresponding to a (state, terminal symbol) pair.
-	Action(state int, terminal int) int
-
-	// GoTo returns a GOTO entry corresponding to a (state, non-terminal symbol) pair.
-	GoTo(state int, lhs int) int
-
-	// ErrorTrapperState returns true when a state can shift the error symbol.
-	ErrorTrapperState(state int) bool
-
-	// LHS returns a LHS symbol of a production.
-	LHS(prod int) int
-
-	// AlternativeSymbolCount returns a symbol count of p production.
-	AlternativeSymbolCount(prod int) int
-
-	// RecoverProduction returns true when a production has the recover directive.
-	RecoverProduction(prod int) bool
-
-	// NonTerminal retuns a string representaion of a non-terminal symbol.
-	NonTerminal(nonTerminal int) string
-
-	// TerminalCount returns a terminal symbol count of grammar.
-	TerminalCount() int
-
-	// SkipTerminal returns true when a terminal symbol must be skipped on syntax analysis.
-	SkipTerminal(terminal int) bool
-
-	// EOF returns the EOF symbol.
-	EOF() int
-
-	// Error returns the error symbol.
-	Error() int
-
-	// Terminal retuns a string representaion of a terminal symbol.
-	Terminal(terminal int) string
-
-	// ASTAction returns an AST action entries.
-	ASTAction(prod int) []int
-}
-
-type VToken interface {
-	// TerminalID returns a terminal ID.
-	TerminalID() int
-
-	// Lexeme returns a lexeme.
-	Lexeme() []byte
-
-	// EOF returns true when a token represents EOF.
-	EOF() bool
-
-	// Invalid returns true when a token is invalid.
-	Invalid() bool
-
-	// BytePosition returns (position, length) pair.
-	// `position` is a byte position where a token appears and `length` is a length in bytes.
-	BytePosition() (int, int)
-
-	// Position returns (row, column) pair.
-	Position() (int, int)
-}
-
-type TokenStream interface {
-	Next() (VToken, error)
-}
-
-type SyntaxError struct {
-	Row               int
-	Col               int
-	Message           string
-	Token             VToken
-	ExpectedTerminals []string
-}
-
-type ParserOption func(p *Parser) error
-
-// DisableLAC disables LAC (lookahead correction). LAC is enabled by default.
-func DisableLAC() ParserOption {
-	return func(p *Parser) error {
-		p.disableLAC = true
-		return nil
-	}
-}
-
-func SemanticAction(semAct SemanticActionSet) ParserOption {
-	return func(p *Parser) error {
-		p.semAct = semAct
-		return nil
-	}
-}
-
-type Parser struct {
-	toks       TokenStream
-	gram       Grammar
-	stateStack *stateStack
-	semAct     SemanticActionSet
-	disableLAC bool
-	onError    bool
-	shiftCount int
-	synErrs    []*SyntaxError
-}
-
-func NewParser(toks TokenStream, gram Grammar, opts ...ParserOption) (*Parser, error) {
-	p := &Parser{
-		toks:       toks,
-		gram:       gram,
-		stateStack: &stateStack{},
-	}
-
-	for _, opt := range opts {
-		err := opt(p)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	return p, nil
-}
-
-func (p *Parser) Parse() error {
-	p.stateStack.push(p.gram.InitialState())
-	tok, err := p.nextToken()
-	if err != nil {
-		return err
-	}
-
-ACTION_LOOP:
-	for {
-		act := p.lookupAction(tok)
-
-		switch {
-		case act < 0: // Shift
-			nextState := act * -1
-
-			recovered := false
-			if p.onError {
-				p.shiftCount++
-
-				// When the parser performs shift three times, the parser recovers from the error state.
-				if p.shiftCount >= 3 {
-					p.onError = false
-					p.shiftCount = 0
-					recovered = true
-				}
-			}
-
-			p.shift(nextState)
-
-			if p.semAct != nil {
-				p.semAct.Shift(tok, recovered)
-			}
-
-			tok, err = p.nextToken()
-			if err != nil {
-				return err
-			}
-		case act > 0: // Reduce
-			prodNum := act
-
-			recovered := false
-			if p.onError && p.gram.RecoverProduction(prodNum) {
-				p.onError = false
-				p.shiftCount = 0
-				recovered = true
-			}
-
-			accepted := p.reduce(prodNum)
-			if accepted {
-				if p.semAct != nil {
-					p.semAct.Accept()
-				}
-
-				return nil
-			}
-
-			if p.semAct != nil {
-				p.semAct.Reduce(prodNum, recovered)
-			}
-		default: // Error
-			if p.onError {
-				tok, err = p.nextToken()
-				if err != nil {
-					return err
-				}
-				if tok.EOF() {
-					if p.semAct != nil {
-						p.semAct.MissError(tok)
-					}
-
-					return nil
-				}
-
-				continue ACTION_LOOP
-			}
-
-			row, col := tok.Position()
-			p.synErrs = append(p.synErrs, &SyntaxError{
-				Row:               row,
-				Col:               col,
-				Message:           "unexpected token",
-				Token:             tok,
-				ExpectedTerminals: p.searchLookahead(p.stateStack.top()),
-			})
-
-			count, ok := p.trapError()
-			if !ok {
-				if p.semAct != nil {
-					p.semAct.MissError(tok)
-				}
-
-				return nil
-			}
-
-			p.onError = true
-			p.shiftCount = 0
-
-			act, err := p.lookupActionOnError()
-			if err != nil {
-				return err
-			}
-
-			p.shift(act * -1)
-
-			if p.semAct != nil {
-				p.semAct.TrapAndShiftError(tok, count)
-			}
-		}
-	}
-}
-
-// validateLookahead validates whether `term` is a valid lookahead in the current context. When `term` is valid,
-// this method returns `true`.
-func (p *Parser) validateLookahead(term int) bool {
-	p.stateStack.enableExploratoryMode()
-	defer p.stateStack.disableExploratoryMode()
-
-	for {
-		act := p.gram.Action(p.stateStack.topExploratorily(), term)
-
-		switch {
-		case act < 0: // Shift
-			return true
-		case act > 0: // Reduce
-			prodNum := act
-
-			lhs := p.gram.LHS(prodNum)
-			if lhs == p.gram.LHS(p.gram.StartProduction()) {
-				return true
-			}
-			n := p.gram.AlternativeSymbolCount(prodNum)
-			p.stateStack.popExploratorily(n)
-			state := p.gram.GoTo(p.stateStack.topExploratorily(), lhs)
-			p.stateStack.pushExploratorily(state)
-		default: // Error
-			return false
-		}
-	}
-}
-
-func (p *Parser) nextToken() (VToken, error) {
-	for {
-		// We don't have to check whether the token is invalid because the kind ID of the invalid token is 0,
-		// and the parsing table doesn't have an entry corresponding to the kind ID 0. Thus we can detect
-		// a syntax error because the parser cannot find an entry corresponding to the invalid token.
-		tok, err := p.toks.Next()
-		if err != nil {
-			return nil, err
-		}
-
-		if p.gram.SkipTerminal(tok.TerminalID()) {
-			continue
-		}
-
-		return tok, nil
-	}
-}
-
-func (p *Parser) tokenToTerminal(tok VToken) int {
-	if tok.EOF() {
-		return p.gram.EOF()
-	}
-
-	return tok.TerminalID()
-}
-
-func (p *Parser) lookupAction(tok VToken) int {
-	if !p.disableLAC {
-		term := p.tokenToTerminal(tok)
-		if !p.validateLookahead(term) {
-			return 0
-		}
-	}
-
-	return p.gram.Action(p.stateStack.top(), p.tokenToTerminal(tok))
-}
-
-func (p *Parser) lookupActionOnError() (int, error) {
-	act := p.gram.Action(p.stateStack.top(), p.gram.Error())
-	if act >= 0 {
-		return 0, fmt.Errorf("an entry must be a shift action by the error symbol; entry: %v, state: %v, symbol: %v", act, p.stateStack.top(), p.gram.Terminal(p.gram.Error()))
-	}
-
-	return act, nil
-}
-
-func (p *Parser) shift(nextState int) {
-	p.stateStack.push(nextState)
-}
-
-func (p *Parser) reduce(prodNum int) bool {
-	lhs := p.gram.LHS(prodNum)
-	if lhs == p.gram.LHS(p.gram.StartProduction()) {
-		return true
-	}
-	n := p.gram.AlternativeSymbolCount(prodNum)
-	p.stateStack.pop(n)
-	nextState := p.gram.GoTo(p.stateStack.top(), lhs)
-	p.stateStack.push(nextState)
-	return false
-}
-
-func (p *Parser) trapError() (int, bool) {
-	count := 0
-	for {
-		if p.gram.ErrorTrapperState(p.stateStack.top()) {
-			return count, true
-		}
-
-		if p.stateStack.top() != p.gram.InitialState() {
-			p.stateStack.pop(1)
-			count++
-		} else {
-			return 0, false
-		}
-	}
-}
-
-func (p *Parser) SyntaxErrors() []*SyntaxError {
-	return p.synErrs
-}
-
-func (p *Parser) searchLookahead(state int) []string {
-	kinds := []string{}
-	termCount := p.gram.TerminalCount()
-	for term := 0; term < termCount; term++ {
-		if p.disableLAC {
-			if p.gram.Action(p.stateStack.top(), term) == 0 {
-				continue
-			}
-		} else {
-			if !p.validateLookahead(term) {
-				continue
-			}
-		}
-
-		// We don't add the error symbol to the look-ahead symbols because users cannot input the error symbol
-		// intentionally.
-		if term == p.gram.Error() {
-			continue
-		}
-
-		kinds = append(kinds, p.gram.Terminal(term))
-	}
-
-	return kinds
-}
-
-type stateStack struct {
-	items    []int
-	itemsExp []int
-}
-
-func (s *stateStack) enableExploratoryMode() {
-	s.itemsExp = make([]int, len(s.items))
-	copy(s.itemsExp, s.items)
-}
-
-func (s *stateStack) disableExploratoryMode() {
-	s.itemsExp = nil
-}
-
-func (s *stateStack) top() int {
-	return s.items[len(s.items)-1]
-}
-
-func (s *stateStack) topExploratorily() int {
-	return s.itemsExp[len(s.itemsExp)-1]
-}
-
-func (s *stateStack) push(state int) {
-	s.items = append(s.items, state)
-}
-
-func (s *stateStack) pushExploratorily(state int) {
-	s.itemsExp = append(s.itemsExp, state)
-}
-
-func (s *stateStack) pop(n int) {
-	s.items = s.items[:len(s.items)-n]
-}
-
-func (s *stateStack) popExploratorily(n int) {
-	s.itemsExp = s.itemsExp[:len(s.itemsExp)-n]
-}
diff --git a/driver/parser/parser_test.go b/driver/parser/parser_test.go
deleted file mode 100644
index cdfd922..0000000
--- a/driver/parser/parser_test.go
+++ /dev/null
@@ -1,833 +0,0 @@
-package parser
-
-import (
-	"fmt"
-	"strings"
-	"testing"
-
-	"grammar"
-	"spec/grammar/parser"
-)
-
-func termNode(kind string, text string, children ...*Node) *Node {
-	return &Node{
-		Type:     NodeTypeTerminal,
-		KindName: kind,
-		Text:     text,
-		Children: children,
-	}
-}
-
-func errorNode() *Node {
-	return &Node{
-		Type:     NodeTypeError,
-		KindName: "error",
-	}
-}
-
-func nonTermNode(kind string, children ...*Node) *Node {
-	return &Node{
-		Type:     NodeTypeNonTerminal,
-		KindName: kind,
-		Children: children,
-	}
-}
-
-func TestParser_Parse(t *testing.T) {
-	tests := []struct {
-		specSrc string
-		src     string
-		synErr  bool
-		cst     *Node
-		ast     *Node
-	}{
-		{
-			specSrc: `
-#name test;
-
-expr
-    : expr add term
-    | term
-    ;
-term
-    : term mul factor
-    | factor
-    ;
-factor
-    : l_paren expr r_paren
-    | id
-    ;
-
-add
-    : '+';
-mul
-    : '*';
-l_paren
-    : '(';
-r_paren
-    : ')';
-id
-    : "[A-Za-z_][0-9A-Za-z_]*";
-`,
-			src: `(a+(b+c))*d+e`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("term",
-						nonTermNode("term",
-							nonTermNode("factor",
-								termNode("l_paren", "("),
-								nonTermNode("expr",
-									nonTermNode("expr",
-										nonTermNode("term",
-											nonTermNode("factor",
-												termNode("id", "a"),
-											),
-										),
-									),
-									termNode("add", "+"),
-									nonTermNode("term",
-										nonTermNode("factor",
-											termNode("l_paren", "("),
-											nonTermNode("expr",
-												nonTermNode("expr",
-													nonTermNode("term",
-														nonTermNode("factor",
-															termNode("id", "b"),
-														),
-													),
-												),
-												termNode("add", "+"),
-												nonTermNode("term",
-													nonTermNode("factor",
-														termNode("id", "c"),
-													),
-												),
-											),
-											termNode("r_paren", ")"),
-										),
-									),
-								),
-								termNode("r_paren", ")"),
-							),
-						),
-						termNode("mul", "*"),
-						nonTermNode("factor",
-							termNode("id", "d"),
-						),
-					),
-				),
-				termNode("add", "+"),
-				nonTermNode("term",
-					nonTermNode("factor",
-						termNode("id", "e"),
-					),
-				),
-			),
-		},
-		// Fragments (\f{}), code point expressions (\u{}), and character property expressions (\p{}) are
-		// not allowed in string literals.
-		{
-			specSrc: `
-#name test;
-
-s
-    : a b c
-    ;
-
-a
-    : '\f{foo}';
-b
-    : '\u{0000}';
-c
-    : '\p{gc=Letter}';
-`,
-			src: `\f{foo}\u{0000}\p{gc=Letter}`,
-			cst: nonTermNode("s",
-				termNode("a", `\f{foo}`),
-				termNode("b", `\u{0000}`),
-				termNode("c", `\p{gc=Letter}`),
-			),
-		},
-		// The driver can reduce productions that have the empty alternative and can generate a CST (and AST) node.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar
-    ;
-foo
-    :
-    ;
-bar
-    : bar_text
-    |
-    ;
-bar_text: "bar";
-`,
-			src: ``,
-			cst: nonTermNode("s",
-				nonTermNode("foo"),
-				nonTermNode("bar"),
-			),
-		},
-		// The driver can reduce productions that have the empty alternative and can generate a CST (and AST) node.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar
-    ;
-foo
-    :
-    ;
-bar
-    : bar_text
-    |
-    ;
-
-bar_text
-    : "bar";
-`,
-			src: `bar`,
-			cst: nonTermNode("s",
-				nonTermNode("foo"),
-				nonTermNode("bar",
-					termNode("bar_text", "bar"),
-				),
-			),
-		},
-		// A production can have multiple alternative productions.
-		{
-			specSrc: `
-#name test;
-
-#prec (
-    #assign $uminus
-    #left mul div
-    #left add sub
-);
-
-expr
-    : expr add expr
-    | expr sub expr
-    | expr mul expr
-    | expr div expr
-    | int
-    | sub int #prec $uminus // This 'sub' means the unary minus symbol.
-    ;
-
-int
-    : "0|[1-9][0-9]*";
-add
-    : '+';
-sub
-    : '-';
-mul
-    : '*';
-div
-    : '/';
-`,
-			src: `-1*-2+3-4/5`,
-			ast: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("expr",
-						nonTermNode("expr",
-							termNode("sub", "-"),
-							termNode("int", "1"),
-						),
-						termNode("mul", "*"),
-						nonTermNode("expr",
-							termNode("sub", "-"),
-							termNode("int", "2"),
-						),
-					),
-					termNode("add", "+"),
-					nonTermNode("expr",
-						termNode("int", "3"),
-					),
-				),
-				termNode("sub", "-"),
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("int", "4"),
-					),
-					termNode("div", "/"),
-					nonTermNode("expr",
-						termNode("int", "5"),
-					),
-				),
-			),
-		},
-		// A lexical production can have multiple production directives.
-		{
-			specSrc: `
-#name test;
-
-s
-    : push_a push_b pop pop
-    ;
-
-push_a #mode default #push a
-    : '->a';
-push_b #mode a #push b
-    : '->b';
-pop #mode a b #pop
-    : '<-';
-`,
-			src: `->a->b<-<-`,
-			ast: nonTermNode("s",
-				termNode("push_a", "->a"),
-				termNode("push_b", "->b"),
-				termNode("pop", "<-"),
-				termNode("pop", "<-"),
-			),
-		},
-		{
-			specSrc: `
-#name test;
-
-mode_tran_seq
-    : mode_tran_seq mode_tran
-    | mode_tran
-    ;
-mode_tran
-    : push_m1
-    | push_m2
-    | pop_m1
-    | pop_m2
-    ;
-
-push_m1 #push m1
-    : "->";
-push_m2 #mode m1 #push m2
-    : "-->";
-pop_m1 #mode m1 #pop
-    : "<-";
-pop_m2 #mode m2 #pop
-    : "<--";
-whitespace #mode default m1 m2 #skip
-    : "\u{0020}+";
-`,
-			src: ` -> --> <-- <- `,
-		},
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar
-    ;
-
-foo
-    : "foo";
-bar #mode default
-    : "bar";
-`,
-			src: `foobar`,
-		},
-		// When #push and #pop are applied to the same symbol, #pop will run first, then #push.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar baz
-    ;
-
-foo #push m1
-    : 'foo';
-bar #mode m1 #pop #push m2
-    : 'bar';
-baz #mode m2
-    : 'baz';
-`,
-			src: `foobarbaz`,
-			ast: nonTermNode("s",
-				termNode("foo", "foo"),
-				termNode("bar", "bar"),
-				termNode("baz", "baz"),
-			),
-		},
-		// When #push and #pop are applied to the same symbol, #pop will run first, then #push, even if #push appears first
-		// in a definition. That is, the order in which #push and #pop appear in grammar has nothing to do with the order in which
-		// they are executed.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar baz
-    ;
-
-foo #push m1
-    : 'foo';
-bar #mode m1 #push m2 #pop
-    : 'bar';
-baz #mode m2
-    : 'baz';
-`,
-			src: `foobarbaz`,
-			ast: nonTermNode("s",
-				termNode("foo", "foo"),
-				termNode("bar", "bar"),
-				termNode("baz", "baz"),
-			),
-		},
-		// The parser can skips specified tokens.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo bar
-    ;
-
-foo
-    : "foo";
-bar
-    : "bar";
-white_space #skip
-    : "[\u{0009}\u{0020}]+";
-`,
-			src: `foo bar`,
-		},
-		// A grammar can contain fragments.
-		{
-			specSrc: `
-#name test;
-
-s
-    : tagline
-    ;
-tagline
-    : "\f{words} IS OUT THERE.";
-fragment words
-    : "[A-Za-z\u{0020}]+";
-`,
-			src: `THE TRUTH IS OUT THERE.`,
-		},
-		// A grammar can contain ast actions.
-		{
-			specSrc: `
-#name test;
-
-list
-    : l_bracket elems r_bracket #ast elems...
-    ;
-elems
-    : elems comma id #ast elems... id
-    | id
-    ;
-
-whitespace #skip
-    : "\u{0020}+";
-l_bracket
-    : '[';
-r_bracket
-    : ']';
-comma
-    : ',';
-id
-    : "[A-Za-z]+";
-`,
-			src: `[Byers, Frohike, Langly]`,
-			cst: nonTermNode("list",
-				termNode("x_1", "["),
-				nonTermNode("elems",
-					nonTermNode("elems",
-						nonTermNode("elems",
-							termNode("id", "Byers"),
-						),
-						termNode("x_3", ","),
-						termNode("id", "Frohike"),
-					),
-					termNode("x_3", ","),
-					termNode("id", "Langly"),
-				),
-				termNode("x_2", "]"),
-			),
-			ast: nonTermNode("list",
-				termNode("id", "Byers"),
-				termNode("id", "Frohike"),
-				termNode("id", "Langly"),
-			),
-		},
-		// The '...' operator can expand child nodes.
-		{
-			specSrc: `
-#name test;
-
-s
-    : a #ast a...
-    ;
-a
-    : a comma foo #ast a... foo
-    | foo
-    ;
-
-comma
-    : ',';
-foo
-    : 'foo';
-`,
-			src: `foo,foo,foo`,
-			ast: nonTermNode("s",
-				termNode("foo", "foo"),
-				termNode("foo", "foo"),
-				termNode("foo", "foo"),
-			),
-		},
-		// The '...' operator also can applied to an element having no children.
-		{
-			specSrc: `
-#name test;
-
-s
-    : a semi_colon #ast a...
-    ;
-a
-    :
-    ;
-
-semi_colon
-    : ';';
-`,
-			src: `;`,
-			ast: nonTermNode("s"),
-		},
-		// A label can be a parameter of #ast directive.
-		{
-			specSrc: `
-#name test;
-
-#prec (
-    #left add sub
-);
-
-expr
-    : expr@lhs add expr@rhs #ast add lhs rhs
-    | expr@lhs sub expr@rhs #ast sub lhs rhs
-    | num
-    ;
-
-add
-    : '+';
-sub
-    : '-';
-num
-    : "0|[1-9][0-9]*";
-`,
-			src: `1+2-3`,
-			ast: nonTermNode("expr",
-				termNode("sub", "-"),
-				nonTermNode("expr",
-					termNode("add", "+"),
-					nonTermNode("expr",
-						termNode("num", "1"),
-					),
-					nonTermNode("expr",
-						termNode("num", "2"),
-					),
-				),
-				nonTermNode("expr",
-					termNode("num", "3"),
-				),
-			),
-		},
-		// An AST can contain a symbol name, even if the symbol has a label. That is, unused labels are allowed.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo@x semi_colon #ast foo
-    ;
-
-semi_colon
-    : ';';
-foo
-    : 'foo';
-`,
-			src: `foo;`,
-			ast: nonTermNode("s",
-				termNode("foo", "foo"),
-			),
-		},
-		// A production has the same precedence and associativity as the right-most terminal symbol.
-		{
-			specSrc: `
-#name test;
-
-#prec (
-    #left add
-);
-
-expr
-    : expr add expr // This alternative has the same precedence and associativiry as 'add'.
-    | int
-    ;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-int
-    : "0|[1-9][0-9]*";
-add
-    : '+';
-`,
-			// This source is recognized as the following structure because the production `expr → expr add expr` has the same
-			// precedence and associativity as the symbol 'add'.
-			//
-			// ((1+2)+3)
-			//
-			// If the symbol doesn't have the precedence and left associativity, the production also doesn't have the precedence
-			// and associativity and this source will be recognized as the following structure.
-			//
-			// (1+(2+3))
-			src: `1+2+3`,
-			ast: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("int", "1"),
-					),
-					termNode("add", "+"),
-					nonTermNode("expr",
-						termNode("int", "2"),
-					),
-				),
-				termNode("add", "+"),
-				nonTermNode("expr",
-					termNode("int", "3"),
-				),
-			),
-		},
-		// The 'prec' directive can set precedence of a production.
-		{
-			specSrc: `
-#name test;
-
-#prec (
-    #assign $uminus
-    #left mul div
-    #left add sub
-);
-
-expr
-    : expr add expr
-    | expr sub expr
-    | expr mul expr
-    | expr div expr
-    | int
-    | sub int #prec $uminus // This 'sub' means a unary minus symbol.
-    ;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-int
-    : "0|[1-9][0-9]*";
-add
-    : '+';
-sub
-    : '-';
-mul
-    : '*';
-div
-    : '/';
-`,
-			// This source is recognized as the following structure because the production `expr → sub expr`
-			// has the `#prec mul` directive and has the same precedence of the symbol `mul`.
-			//
-			// (((-1) * 20) / 5)
-			//
-			// If the production doesn't have the `#prec` directive, this source will be recognized as
-			// the following structure.
-			//
-			// (- ((1 * 20) / 5))
-			src: `-1*20/5`,
-			cst: nonTermNode("expr",
-				nonTermNode("expr",
-					nonTermNode("expr",
-						termNode("sub", "-"),
-						termNode("int", "1"),
-					),
-					termNode("mul", "*"),
-					nonTermNode("expr",
-						termNode("int", "20"),
-					),
-				),
-				termNode("div", "/"),
-				nonTermNode("expr",
-					termNode("int", "5"),
-				),
-			),
-		},
-		// The grammar can contain the 'error' symbol.
-		{
-			specSrc: `
-#name test;
-
-s
-    : id id id semi_colon
-    | error semi_colon
-    ;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semi_colon
-    : ';';
-id
-    : "[A-Za-z_]+";
-`,
-			src: `foo bar baz ;`,
-		},
-		// The 'error' symbol can appear in an #ast directive.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo semi_colon
-    | error semi_colon #ast error
-    ;
-
-semi_colon
-    : ';';
-foo
-    : 'foo';
-`,
-			src:    `bar;`,
-			synErr: true,
-			ast: nonTermNode("s",
-				errorNode(),
-			),
-		},
-		// The 'error' symbol can have a label, and an #ast can reference it.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo semi_colon
-    | error@e semi_colon #ast e
-    ;
-
-semi_colon
-    : ';';
-foo
-    : 'foo';
-`,
-			src:    `bar;`,
-			synErr: true,
-			ast: nonTermNode("s",
-				errorNode(),
-			),
-		},
-		// The grammar can contain the 'recover' directive.
-		{
-			specSrc: `
-#name test;
-
-seq
-    : seq elem
-    | elem
-    ;
-elem
-    : id id id semi_colon
-    | error semi_colon #recover
-    ;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semi_colon
-    : ';';
-id
-    : "[A-Za-z_]+";
-`,
-			src: `a b c ; d e f ;`,
-		},
-		// The same label can be used between different alternatives.
-		{
-			specSrc: `
-#name test;
-
-s
-    : foo@x bar
-    | foo@x
-    ;
-
-foo: 'foo';
-bar: 'bar';
-`,
-			src: `foo`,
-		},
-	}
-
-	for i, tt := range tests {
-		t.Run(fmt.Sprintf("#%v", i), func(t *testing.T) {
-			ast, err := parser.Parse(strings.NewReader(tt.specSrc))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			b := grammar.GrammarBuilder{
-				AST: ast,
-			}
-			cg, _, err := b.Build()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			toks, err := NewTokenStream(cg, strings.NewReader(tt.src))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			gram := NewGrammar(cg)
-			tb := NewDefaultSyntaxTreeBuilder()
-			var opt []ParserOption
-			switch {
-			case tt.ast != nil:
-				opt = append(opt, SemanticAction(NewASTActionSet(gram, tb)))
-			case tt.cst != nil:
-				opt = append(opt, SemanticAction(NewCSTActionSet(gram, tb)))
-			}
-			p, err := NewParser(toks, gram, opt...)
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			err = p.Parse()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			if !tt.synErr && len(p.SyntaxErrors()) > 0 {
-				for _, synErr := range p.SyntaxErrors() {
-					t.Fatalf("unexpected syntax errors occurred: %v", synErr)
-				}
-			}
-
-			switch {
-			case tt.ast != nil:
-				testTree(t, tb.Tree(), tt.ast)
-			case tt.cst != nil:
-				testTree(t, tb.Tree(), tt.cst)
-			}
-		})
-	}
-}
-
-func testTree(t *testing.T, node, expected *Node) {
-	t.Helper()
-
-	if node.Type != expected.Type || node.KindName != expected.KindName || node.Text != expected.Text {
-		t.Fatalf("unexpected node; want: %+v, got: %+v", expected, node)
-	}
-	if len(node.Children) != len(expected.Children) {
-		t.Fatalf("unexpected children; want: %v, got: %v", len(expected.Children), len(node.Children))
-	}
-	for i, c := range node.Children {
-		testTree(t, c, expected.Children[i])
-	}
-}
diff --git a/driver/parser/semantic_action.go b/driver/parser/semantic_action.go
deleted file mode 100644
index 6bb78cf..0000000
--- a/driver/parser/semantic_action.go
+++ /dev/null
@@ -1,371 +0,0 @@
-package parser
-
-import (
-	"encoding/json"
-	"fmt"
-	"io"
-	"strconv"
-)
-
-// SemanticActionSet is a set of semantic actions a parser calls.
-type SemanticActionSet interface {
-	// Shift runs when the parser shifts a symbol onto a state stack. `tok` is a token corresponding to the symbol.
-	// When the parser recovered from an error state by shifting the token, `recovered` is true.
-	Shift(tok VToken, recovered bool)
-
-	// Reduce runs when the parser reduces an RHS of a production to its LHS. `prodNum` is a number of the production.
-	// When the parser recovered from an error state by reducing the production, `recovered` is true.
-	Reduce(prodNum int, recovered bool)
-
-	// Accept runs when the parser accepts an input.
-	Accept()
-
-	// TrapAndShiftError runs when the parser traps a syntax error and shifts a error symbol onto the state stack.
-	// `cause` is a token that caused a syntax error. `popped` is the number of frames that the parser discards
-	// from the state stack.
-	// Unlike `Shift` function, this function doesn't take a token to be shifted as an argument because a token
-	// corresponding to the error symbol doesn't exist.
-	TrapAndShiftError(cause VToken, popped int)
-
-	// MissError runs when the parser fails to trap a syntax error. `cause` is a token that caused a syntax error.
-	MissError(cause VToken)
-}
-
-var _ SemanticActionSet = &SyntaxTreeActionSet{}
-
-// SyntaxTreeNode is a node of a syntax tree. A node type used in SyntaxTreeActionSet must implement SyntaxTreeNode interface.
-type SyntaxTreeNode interface {
-	// ChildCount returns a child count of a node. A parser calls this method to know the child count to be expanded by an `#ast`
-	// directive with `...` operator.
-	ChildCount() int
-
-	// ExpandChildren returns children of a node. A parser calls this method to fetch the children to be expanded by an `#ast`
-	// directive with `...` operator.
-	ExpandChildren() []SyntaxTreeNode
-}
-
-var _ SyntaxTreeNode = &Node{}
-
-// SyntaxTreeBuilder allows you to construct a syntax tree containing arbitrary user-defined node types.
-// The parser uses SyntaxTreeBuilder interface as a part of semantic actions via SyntaxTreeActionSet interface.
-type SyntaxTreeBuilder interface {
-	Shift(kindName string, tok VToken) SyntaxTreeNode
-	ShiftError(kindName string) SyntaxTreeNode
-	Reduce(kindName string, children []SyntaxTreeNode) SyntaxTreeNode
-	Accept(f SyntaxTreeNode)
-}
-
-var _ SyntaxTreeBuilder = &DefaultSyntaxTreeBuilder{}
-
-// DefaultSyntaxTreeBuilder is a implementation of SyntaxTreeBuilder.
-type DefaultSyntaxTreeBuilder struct {
-	tree *Node
-}
-
-// NewDefaultSyntaxTreeBuilder returns a new DefaultSyntaxTreeBuilder.
-func NewDefaultSyntaxTreeBuilder() *DefaultSyntaxTreeBuilder {
-	return &DefaultSyntaxTreeBuilder{}
-}
-
-// Shift is a implementation of SyntaxTreeBuilder.Shift.
-func (b *DefaultSyntaxTreeBuilder) Shift(kindName string, tok VToken) SyntaxTreeNode {
-	bytePos, byteLen := tok.BytePosition()
-	row, col := tok.Position()
-	return &Node{
-		Type:     NodeTypeTerminal,
-		KindName: kindName,
-		Text:     string(tok.Lexeme()),
-		BytePos:  bytePos,
-		ByteLen:  byteLen,
-		Row:      row,
-		Col:      col,
-	}
-}
-
-// ShiftError is a implementation of SyntaxTreeBuilder.ShiftError.
-func (b *DefaultSyntaxTreeBuilder) ShiftError(kindName string) SyntaxTreeNode {
-	return &Node{
-		Type:     NodeTypeError,
-		KindName: kindName,
-	}
-}
-
-// Reduce is a implementation of SyntaxTreeBuilder.Reduce.
-func (b *DefaultSyntaxTreeBuilder) Reduce(kindName string, children []SyntaxTreeNode) SyntaxTreeNode {
-	cNodes := make([]*Node, len(children))
-	for i, c := range children {
-		cNodes[i] = c.(*Node)
-	}
-	return &Node{
-		Type:     NodeTypeNonTerminal,
-		KindName: kindName,
-		Children: cNodes,
-	}
-}
-
-// Accept is a implementation of SyntaxTreeBuilder.Accept.
-func (b *DefaultSyntaxTreeBuilder) Accept(f SyntaxTreeNode) {
-	b.tree = f.(*Node)
-}
-
-// Tree returns a syntax tree when the parser has accepted an input. If a syntax error occurs, the return value is nil.
-func (b *DefaultSyntaxTreeBuilder) Tree() *Node {
-	return b.tree
-}
-
-// SyntaxTreeActionSet is a implementation of SemanticActionSet interface and constructs a syntax tree.
-type SyntaxTreeActionSet struct {
-	gram             Grammar
-	builder          SyntaxTreeBuilder
-	semStack         *semanticStack
-	disableASTAction bool
-}
-
-// NewASTActionSet returns a new SyntaxTreeActionSet that constructs an AST (Abstract Syntax Tree).
-// When grammar `gram` contains `#ast` directives, the new SyntaxTreeActionSet this function returns interprets them.
-func NewASTActionSet(gram Grammar, builder SyntaxTreeBuilder) *SyntaxTreeActionSet {
-	return &SyntaxTreeActionSet{
-		gram:     gram,
-		builder:  builder,
-		semStack: newSemanticStack(),
-	}
-}
-
-// NewCSTTActionSet returns a new SyntaxTreeActionSet that constructs a CST (Concrete Syntax Tree).
-// Even if grammar `gram` contains `#ast` directives, the new SyntaxTreeActionSet this function returns ignores them.
-func NewCSTActionSet(gram Grammar, builder SyntaxTreeBuilder) *SyntaxTreeActionSet {
-	return &SyntaxTreeActionSet{
-		gram:             gram,
-		builder:          builder,
-		semStack:         newSemanticStack(),
-		disableASTAction: true,
-	}
-}
-
-// Shift is a implementation of SemanticActionSet.Shift method.
-func (a *SyntaxTreeActionSet) Shift(tok VToken, recovered bool) {
-	term := a.tokenToTerminal(tok)
-	a.semStack.push(a.builder.Shift(a.gram.Terminal(term), tok))
-}
-
-// Reduce is a implementation of SemanticActionSet.Reduce method.
-func (a *SyntaxTreeActionSet) Reduce(prodNum int, recovered bool) {
-	lhs := a.gram.LHS(prodNum)
-
-	// When an alternative is empty, `n` will be 0, and `handle` will be empty slice.
-	n := a.gram.AlternativeSymbolCount(prodNum)
-	handle := a.semStack.pop(n)
-
-	var astAct []int
-	if !a.disableASTAction {
-		astAct = a.gram.ASTAction(prodNum)
-	}
-	var children []SyntaxTreeNode
-	if astAct != nil {
-		// Count the number of children in advance to avoid frequent growth in a slice for children.
-		{
-			l := 0
-			for _, e := range astAct {
-				if e > 0 {
-					l++
-				} else {
-					offset := e*-1 - 1
-					l += handle[offset].ChildCount()
-				}
-			}
-
-			children = make([]SyntaxTreeNode, l)
-		}
-
-		p := 0
-		for _, e := range astAct {
-			if e > 0 {
-				offset := e - 1
-				children[p] = handle[offset]
-				p++
-			} else {
-				offset := e*-1 - 1
-				for _, c := range handle[offset].ExpandChildren() {
-					children[p] = c
-					p++
-				}
-			}
-		}
-	} else {
-		// If an alternative has no AST action, a driver generates
-		// a node with the same structure as a CST.
-		children = handle
-	}
-
-	a.semStack.push(a.builder.Reduce(a.gram.NonTerminal(lhs), children))
-}
-
-// Accept is a implementation of SemanticActionSet.Accept method.
-func (a *SyntaxTreeActionSet) Accept() {
-	top := a.semStack.pop(1)
-	a.builder.Accept(top[0])
-}
-
-// TrapAndShiftError is a implementation of SemanticActionSet.TrapAndShiftError method.
-func (a *SyntaxTreeActionSet) TrapAndShiftError(cause VToken, popped int) {
-	a.semStack.pop(popped)
-	a.semStack.push(a.builder.ShiftError(a.gram.Terminal(a.gram.Error())))
-}
-
-// MissError is a implementation of SemanticActionSet.MissError method.
-func (a *SyntaxTreeActionSet) MissError(cause VToken) {
-}
-
-func (a *SyntaxTreeActionSet) tokenToTerminal(tok VToken) int {
-	if tok.EOF() {
-		return a.gram.EOF()
-	}
-
-	return tok.TerminalID()
-}
-
-type semanticStack struct {
-	frames []SyntaxTreeNode
-}
-
-func newSemanticStack() *semanticStack {
-	return &semanticStack{
-		frames: make([]SyntaxTreeNode, 0, 100),
-	}
-}
-
-func (s *semanticStack) push(f SyntaxTreeNode) {
-	s.frames = append(s.frames, f)
-}
-
-func (s *semanticStack) pop(n int) []SyntaxTreeNode {
-	fs := s.frames[len(s.frames)-n:]
-	s.frames = s.frames[:len(s.frames)-n]
-
-	return fs
-}
-
-type NodeType int
-
-const (
-	NodeTypeError       = 0
-	NodeTypeTerminal    = 1
-	NodeTypeNonTerminal = 2
-)
-
-// Node is a implementation of SyntaxTreeNode interface.
-type Node struct {
-	Type     NodeType
-	KindName string
-	Text     string
-	BytePos  int
-	ByteLen  int
-	Row      int
-	Col      int
-	Children []*Node
-}
-
-func (n *Node) MarshalJSON() ([]byte, error) {
-	switch n.Type {
-	case NodeTypeError:
-		return json.Marshal(struct {
-			Type     NodeType `json:"type"`
-			KindName string   `json:"kind_name"`
-		}{
-			Type:     n.Type,
-			KindName: n.KindName,
-		})
-	case NodeTypeTerminal:
-		if n.KindName == "" {
-			return json.Marshal(struct {
-				Type NodeType `json:"type"`
-				Text string   `json:"text"`
-				Row  int      `json:"row"`
-				Col  int      `json:"col"`
-			}{
-				Type: n.Type,
-				Text: n.Text,
-				Row:  n.Row,
-				Col:  n.Col,
-			})
-		}
-		return json.Marshal(struct {
-			Type     NodeType `json:"type"`
-			KindName string   `json:"kind_name"`
-			Text     string   `json:"text"`
-			Row      int      `json:"row"`
-			Col      int      `json:"col"`
-		}{
-			Type:     n.Type,
-			KindName: n.KindName,
-			Text:     n.Text,
-			Row:      n.Row,
-			Col:      n.Col,
-		})
-	case NodeTypeNonTerminal:
-		return json.Marshal(struct {
-			Type     NodeType `json:"type"`
-			KindName string   `json:"kind_name"`
-			Children []*Node  `json:"children"`
-		}{
-			Type:     n.Type,
-			KindName: n.KindName,
-			Children: n.Children,
-		})
-	default:
-		return nil, fmt.Errorf("invalid node type: %v", n.Type)
-	}
-}
-
-// ChildCount is a implementation of SyntaxTreeNode.ChildCount.
-func (n *Node) ChildCount() int {
-	return len(n.Children)
-}
-
-// ExpandChildren is a implementation of SyntaxTreeNode.ExpandChildren.
-func (n *Node) ExpandChildren() []SyntaxTreeNode {
-	fs := make([]SyntaxTreeNode, len(n.Children))
-	for i, n := range n.Children {
-		fs[i] = n
-	}
-	return fs
-}
-
-// PrintTree prints a syntax tree whose root is `node`.
-func PrintTree(w io.Writer, node *Node) {
-	printTree(w, node, "", "")
-}
-
-func printTree(w io.Writer, node *Node, ruledLine string, childRuledLinePrefix string) {
-	if node == nil {
-		return
-	}
-
-	switch node.Type {
-	case NodeTypeError:
-		fmt.Fprintf(w, "%v%v\n", ruledLine, node.KindName)
-	case NodeTypeTerminal:
-		fmt.Fprintf(w, "%v%v %v\n", ruledLine, node.KindName, strconv.Quote(node.Text))
-	case NodeTypeNonTerminal:
-		fmt.Fprintf(w, "%v%v\n", ruledLine, node.KindName)
-
-		num := len(node.Children)
-		for i, child := range node.Children {
-			var line string
-			if num > 1 && i < num-1 {
-				line = "├─ "
-			} else {
-				line = "└─ "
-			}
-
-			var prefix string
-			if i >= num-1 {
-				prefix = "   "
-			} else {
-				prefix = "│  "
-			}
-
-			printTree(w, child, childRuledLinePrefix+line, childRuledLinePrefix+prefix)
-		}
-	}
-}
diff --git a/driver/parser/semantic_action_test.go b/driver/parser/semantic_action_test.go
deleted file mode 100644
index 8c224e2..0000000
--- a/driver/parser/semantic_action_test.go
+++ /dev/null
@@ -1,227 +0,0 @@
-package parser
-
-import (
-	"fmt"
-	"strings"
-	"testing"
-
-	"grammar"
-	spec "spec/grammar"
-	"spec/grammar/parser"
-)
-
-type testSemAct struct {
-	gram   *spec.CompiledGrammar
-	actLog []string
-}
-
-func (a *testSemAct) Shift(tok VToken, recovered bool) {
-	t := a.gram.Syntactic.Terminals[tok.TerminalID()]
-	if recovered {
-		a.actLog = append(a.actLog, fmt.Sprintf("shift/%v/recovered", t))
-	} else {
-		a.actLog = append(a.actLog, fmt.Sprintf("shift/%v", t))
-	}
-}
-
-func (a *testSemAct) Reduce(prodNum int, recovered bool) {
-	lhsSym := a.gram.Syntactic.LHSSymbols[prodNum]
-	lhsText := a.gram.Syntactic.NonTerminals[lhsSym]
-	if recovered {
-		a.actLog = append(a.actLog, fmt.Sprintf("reduce/%v/recovered", lhsText))
-	} else {
-		a.actLog = append(a.actLog, fmt.Sprintf("reduce/%v", lhsText))
-	}
-}
-
-func (a *testSemAct) Accept() {
-	a.actLog = append(a.actLog, "accept")
-}
-
-func (a *testSemAct) TrapAndShiftError(cause VToken, popped int) {
-	a.actLog = append(a.actLog, fmt.Sprintf("trap/%v/shift/error", popped))
-}
-
-func (a *testSemAct) MissError(cause VToken) {
-	a.actLog = append(a.actLog, "miss")
-}
-
-func TestParserWithSemanticAction(t *testing.T) {
-	specSrcWithErrorProd := `
-#name test;
-
-seq
-    : seq elem semicolon
-	| elem semicolon
-    | error star star semicolon
-	| error semicolon #recover
-	;
-elem
-    : char char char
-	;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semicolon
-    : ';';
-star
-    : '*';
-char
-    : "[a-z]";
-`
-
-	specSrcWithoutErrorProd := `
-#name test;
-
-seq
-    : seq elem semicolon
-	| elem semicolon
-	;
-elem
-    : char char char
-	;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semicolon
-    : ';';
-char
-    : "[a-z]";
-`
-
-	tests := []struct {
-		caption string
-		specSrc string
-		src     string
-		actLog  []string
-	}{
-		{
-			caption: "when an input contains no syntax error, the driver calls `Shift`, `Reduce`, and `Accept`.",
-			specSrc: specSrcWithErrorProd,
-			src:     `a b c; d e f;`,
-			actLog: []string{
-				"shift/char",
-				"shift/char",
-				"shift/char",
-				"reduce/elem",
-				"shift/semicolon",
-				"reduce/seq",
-
-				"shift/char",
-				"shift/char",
-				"shift/char",
-				"reduce/elem",
-				"shift/semicolon",
-				"reduce/seq",
-
-				"accept",
-			},
-		},
-		{
-			caption: "when a grammar has `error` symbol, the driver calls `TrapAndShiftError`.",
-			specSrc: specSrcWithErrorProd,
-			src:     `a; b !; c d !; e ! * *; h i j;`,
-			actLog: []string{
-				"shift/char",
-				"trap/1/shift/error",
-				"shift/semicolon",
-				"reduce/seq/recovered",
-
-				"shift/char",
-				"trap/2/shift/error",
-				"shift/semicolon",
-				"reduce/seq/recovered",
-
-				"shift/char",
-				"shift/char",
-				"trap/3/shift/error",
-				"shift/semicolon",
-				"reduce/seq/recovered",
-
-				"shift/char",
-				"trap/2/shift/error",
-				"shift/star",
-				"shift/star",
-				// When the driver shifts three times, it recovers from an error.
-				"shift/semicolon/recovered",
-				"reduce/seq",
-
-				"shift/char",
-				"shift/char",
-				"shift/char",
-				"reduce/elem",
-				"shift/semicolon",
-				"reduce/seq",
-
-				// Even if the input contains syntax errors, the driver calls `Accept` when the input is accepted
-				// according to the error production.
-				"accept",
-			},
-		},
-		{
-			caption: "when the input doesn't meet the error production, the driver calls `MissError`.",
-			specSrc: specSrcWithErrorProd,
-			src:     `a !`,
-			actLog: []string{
-				"shift/char",
-				"trap/1/shift/error",
-
-				"miss",
-			},
-		},
-		{
-			caption: "when a syntax error isn't trapped, the driver calls `MissError`.",
-			specSrc: specSrcWithoutErrorProd,
-			src:     `a !`,
-			actLog: []string{
-				"shift/char",
-
-				"miss",
-			},
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.caption, func(t *testing.T) {
-			ast, err := parser.Parse(strings.NewReader(tt.specSrc))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			b := grammar.GrammarBuilder{
-				AST: ast,
-			}
-			gram, _, err := b.Build()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			toks, err := NewTokenStream(gram, strings.NewReader(tt.src))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			semAct := &testSemAct{
-				gram: gram,
-			}
-			p, err := NewParser(toks, NewGrammar(gram), SemanticAction(semAct))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			err = p.Parse()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			if len(semAct.actLog) != len(tt.actLog) {
-				t.Fatalf("unexpected action log; want: %+v, got: %+v", tt.actLog, semAct.actLog)
-			}
-
-			for i, e := range tt.actLog {
-				if semAct.actLog[i] != e {
-					t.Fatalf("unexpected action log; want: %+v, got: %+v", tt.actLog, semAct.actLog)
-				}
-			}
-		})
-	}
-}
diff --git a/driver/parser/spec.go b/driver/parser/spec.go
deleted file mode 100644
index b288f5f..0000000
--- a/driver/parser/spec.go
+++ /dev/null
@@ -1,73 +0,0 @@
-package parser
-
-import spec "spec/grammar"
-
-type grammarImpl struct {
-	g *spec.CompiledGrammar
-}
-
-func NewGrammar(g *spec.CompiledGrammar) *grammarImpl {
-	return &grammarImpl{
-		g: g,
-	}
-}
-
-func (g *grammarImpl) InitialState() int {
-	return g.g.Syntactic.InitialState
-}
-
-func (g *grammarImpl) StartProduction() int {
-	return g.g.Syntactic.StartProduction
-}
-
-func (g *grammarImpl) RecoverProduction(prod int) bool {
-	return g.g.Syntactic.RecoverProductions[prod] != 0
-}
-
-func (g *grammarImpl) Action(state int, terminal int) int {
-	return g.g.Syntactic.Action[state*g.g.Syntactic.TerminalCount+terminal]
-}
-
-func (g *grammarImpl) GoTo(state int, lhs int) int {
-	return g.g.Syntactic.GoTo[state*g.g.Syntactic.NonTerminalCount+lhs]
-}
-
-func (g *grammarImpl) AlternativeSymbolCount(prod int) int {
-	return g.g.Syntactic.AlternativeSymbolCounts[prod]
-}
-
-func (g *grammarImpl) TerminalCount() int {
-	return g.g.Syntactic.TerminalCount
-}
-
-func (g *grammarImpl) SkipTerminal(terminal int) bool {
-	return g.g.Syntactic.TerminalSkip[terminal] == 1
-}
-
-func (g *grammarImpl) ErrorTrapperState(state int) bool {
-	return g.g.Syntactic.ErrorTrapperStates[state] != 0
-}
-
-func (g *grammarImpl) NonTerminal(nonTerminal int) string {
-	return g.g.Syntactic.NonTerminals[nonTerminal]
-}
-
-func (g *grammarImpl) LHS(prod int) int {
-	return g.g.Syntactic.LHSSymbols[prod]
-}
-
-func (g *grammarImpl) EOF() int {
-	return g.g.Syntactic.EOFSymbol
-}
-
-func (g *grammarImpl) Error() int {
-	return g.g.Syntactic.ErrorSymbol
-}
-
-func (g *grammarImpl) Terminal(terminal int) string {
-	return g.g.Syntactic.Terminals[terminal]
-}
-
-func (g *grammarImpl) ASTAction(prod int) []int {
-	return g.g.ASTAction.Entries[prod]
-}
diff --git a/driver/parser/syntax_error_test.go b/driver/parser/syntax_error_test.go
deleted file mode 100644
index c508be6..0000000
--- a/driver/parser/syntax_error_test.go
+++ /dev/null
@@ -1,306 +0,0 @@
-package parser
-
-import (
-	"fmt"
-	"sort"
-	"strings"
-	"testing"
-
-	"grammar"
-	"spec/grammar/parser"
-)
-
-func TestParserWithSyntaxErrors(t *testing.T) {
-	tests := []struct {
-		caption     string
-		specSrc     string
-		src         string
-		synErrCount int
-	}{
-		{
-			caption: "the parser can report a syntax error",
-			specSrc: `
-#name test;
-
-s
-    : foo
-    ;
-
-foo
-    : 'foo';
-`,
-			src:         `bar`,
-			synErrCount: 1,
-		},
-		{
-			caption: "when the parser reduced a production having the reduce directive, the parser will recover from an error state",
-			specSrc: `
-#name test;
-
-seq
-    : seq elem semi_colon
-	| elem semi_colon
-	| error semi_colon #recover
-	;
-elem
-    : a b c
-	;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semi_colon
-    : ';';
-a
-    : 'a';
-b
-    : 'b';
-c
-    : 'c';
-`,
-			src:         `!; a!; ab!;`,
-			synErrCount: 3,
-		},
-		{
-			caption: "After the parser shifts the error symbol, symbols are ignored until a symbol the parser can perform shift appears",
-			specSrc: `
-#name test;
-
-seq
-    : seq elem semi_colon
-	| elem semi_colon
-	| error semi_colon #recover
-	;
-elem
-    : a b c
-	;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semi_colon
-    : ';';
-a
-    : 'a';
-b
-    : 'b';
-c
-    : 'c';
-`,
-			// After the parser trasits to the error state reading the first invalid symbol ('!'),
-			// the second and third invalid symbols ('!') are ignored.
-			src:         `! ! !; a!; ab!;`,
-			synErrCount: 3,
-		},
-		{
-			caption: "when the parser performs shift three times, the parser recovers from the error state",
-			specSrc: `
-#name test;
-
-seq
-    : seq elem semi_colon
-	| elem semi_colon
-	| error star star semi_colon
-	;
-elem
-    : a b c
-	;
-
-ws #skip
-    : "[\u{0009}\u{0020}]+";
-semi_colon
-    : ';';
-star
-    : '*';
-a
-    : 'a';
-b
-    : 'b';
-c
-    : 'c';
-`,
-			src:         `!**; a!**; ab!**; abc!`,
-			synErrCount: 4,
-		},
-	}
-	for i, tt := range tests {
-		t.Run(fmt.Sprintf("#%v", i), func(t *testing.T) {
-			ast, err := parser.Parse(strings.NewReader(tt.specSrc))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			b := grammar.GrammarBuilder{
-				AST: ast,
-			}
-			gram, _, err := b.Build()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			toks, err := NewTokenStream(gram, strings.NewReader(tt.src))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			p, err := NewParser(toks, NewGrammar(gram))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			err = p.Parse()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			synErrs := p.SyntaxErrors()
-			if len(synErrs) != tt.synErrCount {
-				t.Fatalf("unexpected syntax error; want: %v error(s), got: %v error(s)", tt.synErrCount, len(synErrs))
-			}
-		})
-	}
-}
-
-func TestParserWithSyntaxErrorAndExpectedLookahead(t *testing.T) {
-	tests := []struct {
-		caption  string
-		specSrc  string
-		src      string
-		cause    string
-		expected []string
-	}{
-		{
-			caption: "the parser reports an expected lookahead symbol",
-			specSrc: `
-#name test;
-
-s
-    : foo
-    ;
-
-foo
-    : 'foo';
-`,
-			src:   `bar`,
-			cause: `bar`,
-			expected: []string{
-				"foo",
-			},
-		},
-		{
-			caption: "the parser reports expected lookahead symbols",
-			specSrc: `
-#name test;
-
-s
-    : foo
-    | bar
-    ;
-
-foo
-    : 'foo';
-bar
-    : 'bar';
-`,
-			src:   `baz`,
-			cause: `baz`,
-			expected: []string{
-				"foo",
-				"bar",
-			},
-		},
-		{
-			caption: "the parser may report the EOF as an expected lookahead symbol",
-			specSrc: `
-#name test;
-
-s
-    : foo
-    ;
-
-foo
-    : 'foo';
-`,
-			src:   `foobar`,
-			cause: `bar`,
-			expected: []string{
-				"<eof>",
-			},
-		},
-		{
-			caption: "the parser may report the EOF and others as expected lookahead symbols",
-			specSrc: `
-#name test;
-
-s
-    : foo
-    |
-    ;
-
-foo
-    : 'foo';
-`,
-			src:   `bar`,
-			cause: `bar`,
-			expected: []string{
-				"foo",
-				"<eof>",
-			},
-		},
-	}
-	for i, tt := range tests {
-		t.Run(fmt.Sprintf("#%v", i), func(t *testing.T) {
-			ast, err := parser.Parse(strings.NewReader(tt.specSrc))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			b := grammar.GrammarBuilder{
-				AST: ast,
-			}
-			gram, _, err := b.Build()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			toks, err := NewTokenStream(gram, strings.NewReader(tt.src))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			p, err := NewParser(toks, NewGrammar(gram))
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			err = p.Parse()
-			if err != nil {
-				t.Fatal(err)
-			}
-
-			synErrs := p.SyntaxErrors()
-			if synErrs == nil {
-				t.Fatalf("expected one syntax error, but it didn't occur")
-			}
-			if len(synErrs) != 1 {
-				t.Fatalf("too many syntax errors: %v errors", len(synErrs))
-			}
-			synErr := synErrs[0]
-			if string(synErr.Token.Lexeme()) != tt.cause {
-				t.Fatalf("unexpected lexeme: want: %v, got: %v", tt.cause, string(synErr.Token.Lexeme()))
-			}
-			if len(synErr.ExpectedTerminals) != len(tt.expected) {
-				t.Fatalf("unexpected lookahead symbols: want: %v, got: %v", tt.expected, synErr.ExpectedTerminals)
-			}
-			sort.Slice(tt.expected, func(i, j int) bool {
-				return tt.expected[i] < tt.expected[j]
-			})
-			sort.Slice(synErr.ExpectedTerminals, func(i, j int) bool {
-				return synErr.ExpectedTerminals[i] < synErr.ExpectedTerminals[j]
-			})
-			for i, e := range tt.expected {
-				if synErr.ExpectedTerminals[i] != e {
-					t.Errorf("unexpected lookahead symbol: want: %v, got: %v", e, synErr.ExpectedTerminals[i])
-				}
-			}
-		})
-	}
-}
diff --git a/driver/parser/template.go b/driver/parser/template.go
deleted file mode 100644
index 3e25193..0000000
--- a/driver/parser/template.go
+++ /dev/null
@@ -1,535 +0,0 @@
-package parser
-
-import (
-	"bytes"
-	_ "embed"
-	"fmt"
-	"go/ast"
-	"go/format"
-	"go/parser"
-	"go/token"
-	goToken "go/token"
-	"strconv"
-	"strings"
-	"text/template"
-
-	spec "spec/grammar"
-)
-
-// go:embed parser.go
-var parserCoreSrc string
-
-// go:embed semantic_action.go
-var semActSrc string
-
-func GenParser(cgram *spec.CompiledGrammar, pkgName string) ([]byte, error) {
-	var parserSrc string
-	{
-		fset := goToken.NewFileSet()
-		f, err := parser.ParseFile(fset, "parser.go", parserCoreSrc, parser.ParseComments)
-		if err != nil {
-			return nil, err
-		}
-
-		var b strings.Builder
-		err = format.Node(&b, fset, f)
-		if err != nil {
-			return nil, err
-		}
-
-		parserSrc = b.String()
-	}
-
-	var grammarSrc string
-	{
-		t, err := template.New("").Funcs(genGrammarTemplateFuncs(cgram)).Parse(grammarSrcTmplate)
-		if err != nil {
-			return nil, err
-		}
-
-		var b strings.Builder
-		err = t.Execute(&b, map[string]interface{}{
-			"initialState":     cgram.Syntactic.InitialState,
-			"startProduction":  cgram.Syntactic.StartProduction,
-			"terminalCount":    cgram.Syntactic.TerminalCount,
-			"nonTerminalCount": cgram.Syntactic.NonTerminalCount,
-			"eofSymbol":        cgram.Syntactic.EOFSymbol,
-			"errorSymbol":      cgram.Syntactic.ErrorSymbol,
-		})
-		if err != nil {
-			return nil, err
-		}
-
-		grammarSrc = b.String()
-	}
-
-	var lexerSrc string
-	{
-		t, err := template.New("").Funcs(genLexerTemplateFuncs(cgram)).Parse(lexerSrcTmplate)
-		if err != nil {
-			return nil, err
-		}
-
-		var b strings.Builder
-		err = t.Execute(&b, nil)
-		if err != nil {
-			return nil, err
-		}
-
-		lexerSrc = b.String()
-	}
-
-	var src string
-	{
-		tmpl := `// Code generated by vartan-go. DO NOT EDIT.
-{{ .parserSrc }}
-
-{{ .grammarSrc }}
-
-{{ .lexerSrc }}
-`
-		t, err := template.New("").Parse(tmpl)
-		if err != nil {
-			return nil, err
-		}
-
-		var b strings.Builder
-		err = t.Execute(&b, map[string]string{
-			"parserSrc":  parserSrc,
-			"grammarSrc": grammarSrc,
-			"lexerSrc":   lexerSrc,
-		})
-		if err != nil {
-			return nil, err
-		}
-
-		src = b.String()
-	}
-
-	fset := goToken.NewFileSet()
-	f, err := parser.ParseFile(fset, "", src, parser.ParseComments)
-	if err != nil {
-		return nil, err
-	}
-
-	f.Name = ast.NewIdent(pkgName)
-
-	// Complete an import statement.
-	for _, d := range f.Decls {
-		gd, ok := d.(*ast.GenDecl)
-		if !ok || gd.Tok != token.IMPORT {
-			continue
-		}
-		gd.Specs = append(gd.Specs, &ast.ImportSpec{
-			Path: &ast.BasicLit{
-				Value: `"io"`,
-			},
-		})
-		break
-	}
-
-	var b bytes.Buffer
-	err = format.Node(&b, fset, f)
-	if err != nil {
-		return nil, err
-	}
-
-	return b.Bytes(), nil
-}
-
-const grammarSrcTmplate = `
-type grammarImpl struct {
-	recoverProductions      []int
-	action                  []int
-	goTo                    []int
-	alternativeSymbolCounts []int
-	errorTrapperStates      []int
-	nonTerminals            []string
-	lhsSymbols              []int
-	terminals               []string
-	terminalSkip            []int
-	astActions              [][]int
-}
-
-func NewGrammar() *grammarImpl {
-	return &grammarImpl{
-		recoverProductions:      {{ genRecoverProductions }},
-		action:                  {{ genAction }},
-		goTo:                    {{ genGoTo }},
-		alternativeSymbolCounts: {{ genAlternativeSymbolCounts }},
-		errorTrapperStates:      {{ genErrorTrapperStates }},
-		nonTerminals:            {{ genNonTerminals }},
-		lhsSymbols:              {{ genLHSSymbols }},
-		terminals:               {{ genTerminals }},
-		terminalSkip:            {{ genTerminalSkip }},
-		astActions:              {{ genASTActions }},
-	}
-}
-
-func (g *grammarImpl) InitialState() int {
-	return {{ .initialState }}
-}
-
-func (g *grammarImpl) StartProduction() int {
-	return {{ .startProduction }}
-}
-
-func (g *grammarImpl) RecoverProduction(prod int) bool {
-	return g.recoverProductions[prod] != 0
-}
-
-func (g *grammarImpl) Action(state int, terminal int) int {
-	return g.action[state*{{ .terminalCount }}+terminal]
-}
-
-func (g *grammarImpl) GoTo(state int, lhs int) int {
-	return g.goTo[state*{{ .nonTerminalCount }}+lhs]
-}
-
-func (g *grammarImpl) AlternativeSymbolCount(prod int) int {
-	return g.alternativeSymbolCounts[prod]
-}
-
-func (g *grammarImpl) TerminalCount() int {
-	return {{ .terminalCount }}
-}
-
-func (g *grammarImpl) SkipTerminal(terminal int) bool {
-	return g.terminalSkip[terminal] == 1
-}
-
-func (g *grammarImpl) ErrorTrapperState(state int) bool {
-	return g.errorTrapperStates[state] != 0
-}
-
-func (g *grammarImpl) NonTerminal(nonTerminal int) string {
-	return g.nonTerminals[nonTerminal]
-}
-
-func (g *grammarImpl) LHS(prod int) int {
-	return g.lhsSymbols[prod]
-}
-
-func (g *grammarImpl) EOF() int {
-	return {{ .eofSymbol }}
-}
-
-func (g *grammarImpl) Error() int {
-	return {{ .errorSymbol }}
-}
-
-func (g *grammarImpl) Terminal(terminal int) string {
-	return g.terminals[terminal]
-}
-
-func (g *grammarImpl) ASTAction(prod int) []int {
-	return g.astActions[prod]
-}
-`
-
-func genGrammarTemplateFuncs(cgram *spec.CompiledGrammar) template.FuncMap {
-	return template.FuncMap{
-		"genRecoverProductions": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.RecoverProductions {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genAction": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.Action {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genGoTo": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.GoTo {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genAlternativeSymbolCounts": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.AlternativeSymbolCounts {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genErrorTrapperStates": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.ErrorTrapperStates {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genNonTerminals": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]string{\n")
-			for _, v := range cgram.Syntactic.NonTerminals {
-				fmt.Fprintf(&b, "%v,\n", strconv.Quote(v))
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genLHSSymbols": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.LHSSymbols {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genTerminals": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]string{\n")
-			for _, v := range cgram.Syntactic.Terminals {
-				fmt.Fprintf(&b, "%v,\n", strconv.Quote(v))
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genTerminalSkip": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.TerminalSkip {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-		"genASTActions": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[][]int{\n")
-			for _, entries := range cgram.ASTAction.Entries {
-				if len(entries) == 0 {
-					fmt.Fprintf(&b, "nil,\n")
-					continue
-				}
-
-				fmt.Fprintf(&b, "{\n")
-				c := 1
-				for _, v := range entries {
-					fmt.Fprintf(&b, "%v, ", v)
-					if c == 20 {
-						fmt.Fprintf(&b, "\n")
-						c = 1
-					} else {
-						c++
-					}
-				}
-				if c > 1 {
-					fmt.Fprintf(&b, "\n")
-				}
-				fmt.Fprintf(&b, "},\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-	}
-}
-
-const lexerSrcTmplate = `
-type vToken struct {
-	terminalID int
-	tok        *Token
-}
-
-func (t *vToken) TerminalID() int {
-	return t.terminalID
-}
-
-func (t *vToken) Lexeme() []byte {
-	return t.tok.Lexeme
-}
-
-func (t *vToken) EOF() bool {
-	return t.tok.EOF
-}
-
-func (t *vToken) Invalid() bool {
-	return t.tok.Invalid
-}
-
-func (t *vToken) BytePosition() (int, int) {
-	return t.tok.BytePos, t.tok.ByteLen
-}
-
-func (t *vToken) Position() (int, int) {
-	return t.tok.Row, t.tok.Col
-}
-
-var kindToTerminal = {{ genKindToTerminal }}
-
-type tokenStream struct {
-	lex            *Lexer
-	kindToTerminal []int
-}
-
-func NewTokenStream(src io.Reader) (*tokenStream, error) {
-	lex, err := NewLexer(NewLexSpec(), src)
-	if err != nil {
-		return nil, err
-	}
-
-	return &tokenStream{
-		lex: lex,
-	}, nil
-}
-
-func (t *tokenStream) Next() (VToken, error) {
-	tok, err := t.lex.Next()
-	if err != nil {
-		return nil, err
-	}
-	return &vToken{
-		terminalID: kindToTerminal[tok.KindID],
-		tok:        tok,
-	}, nil
-}
-`
-
-func genLexerTemplateFuncs(cgram *spec.CompiledGrammar) template.FuncMap {
-	return template.FuncMap{
-		"genKindToTerminal": func() string {
-			var b strings.Builder
-			fmt.Fprintf(&b, "[]int{\n")
-			c := 1
-			for _, v := range cgram.Syntactic.KindToTerminal {
-				fmt.Fprintf(&b, "%v, ", v)
-				if c == 20 {
-					fmt.Fprintf(&b, "\n")
-					c = 1
-				} else {
-					c++
-				}
-			}
-			if c > 1 {
-				fmt.Fprintf(&b, "\n")
-			}
-			fmt.Fprintf(&b, "}")
-			return b.String()
-		},
-	}
-}
-
-func GenSemanticAction(pkgName string) ([]byte, error) {
-	var src string
-	{
-		tmpl := `// Code generated by vartan-go. DO NOT EDIT.
-{{ .semActSrc }}
-`
-		t, err := template.New("").Parse(tmpl)
-		if err != nil {
-			return nil, err
-		}
-
-		var b strings.Builder
-		err = t.Execute(&b, map[string]string{
-			"semActSrc": semActSrc,
-		})
-		if err != nil {
-			return nil, err
-		}
-
-		src = b.String()
-	}
-
-	fset := goToken.NewFileSet()
-	f, err := parser.ParseFile(fset, "", src, parser.ParseComments)
-	if err != nil {
-		return nil, err
-	}
-
-	f.Name = ast.NewIdent(pkgName)
-
-	var b bytes.Buffer
-	err = format.Node(&b, fset, f)
-	if err != nil {
-		return nil, err
-	}
-
-	return b.Bytes(), nil
-}
diff --git a/driver/parser/token_stream.go b/driver/parser/token_stream.go
deleted file mode 100644
index b15e8bf..0000000
--- a/driver/parser/token_stream.go
+++ /dev/null
@@ -1,65 +0,0 @@
-package parser
-
-import (
-	"io"
-
-	"driver/lexer"
-	spec "spec/grammar"
-)
-
-type vToken struct {
-	terminalID int
-	tok        *lexer.Token
-}
-
-func (t *vToken) TerminalID() int {
-	return t.terminalID
-}
-
-func (t *vToken) Lexeme() []byte {
-	return t.tok.Lexeme
-}
-
-func (t *vToken) EOF() bool {
-	return t.tok.EOF
-}
-
-func (t *vToken) Invalid() bool {
-	return t.tok.Invalid
-}
-
-func (t *vToken) BytePosition() (int, int) {
-	return t.tok.BytePos, t.tok.ByteLen
-}
-
-func (t *vToken) Position() (int, int) {
-	return t.tok.Row, t.tok.Col
-}
-
-type tokenStream struct {
-	lex            *lexer.Lexer
-	kindToTerminal []int
-}
-
-func NewTokenStream(g *spec.CompiledGrammar, src io.Reader) (TokenStream, error) {
-	lex, err := lexer.NewLexer(lexer.NewLexSpec(g.Lexical), src)
-	if err != nil {
-		return nil, err
-	}
-
-	return &tokenStream{
-		lex:            lex,
-		kindToTerminal: g.Syntactic.KindToTerminal,
-	}, nil
-}
-
-func (l *tokenStream) Next() (VToken, error) {
-	tok, err := l.lex.Next()
-	if err != nil {
-		return nil, err
-	}
-	return &vToken{
-		terminalID: l.kindToTerminal[tok.KindID],
-		tok:        tok,
-	}, nil
-}