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add prefix, and infix operators

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This commit is contained in:
Tommy Parnell
2018-01-14 14:43:26 -05:00
parent d98c02b472
commit eb404145b6
3 changed files with 316 additions and 9 deletions
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100
parser/parser.go
View File

@@ -48,6 +48,20 @@ func New(l *lexer.Lexer) *Parser {
l: l,
errors: []string{},
}
p.infixParseFns = make(map[token.TokenType]infixParseFn)
p.registerInfix(token.PLUS, p.parseInfixExpression)
p.registerInfix(token.MINUS, p.parseInfixExpression)
p.registerInfix(token.SLASH, p.parseInfixExpression)
p.registerInfix(token.ASTERISK, p.parseInfixExpression)
p.registerInfix(token.EQ, p.parseInfixExpression)
p.registerInfix(token.NOT_EQ, p.parseInfixExpression)
p.registerInfix(token.LT, p.parseInfixExpression)
p.registerInfix(token.GT, p.parseInfixExpression)
p.prefixParseFns = make(map[token.TokenType]prefixParseFn)
p.registerPrefix(token.IDENT, p.parseIdentifier)
p.registerPrefix(token.INT, p.parseIntegerLiteral)
p.registerPrefix(token.BANG, p.parsePrefixExpression)
p.registerPrefix(token.MINUS, p.parsePrefixExpression)
// Read two tokens, so curToken and peekToken are both set
p.nextToken()
@@ -56,6 +70,46 @@ func New(l *lexer.Lexer) *Parser {
return p
}
func (p *Parser) parsePrefixExpression() ast.Expression {
expression := &ast.PrefixExpression{
Token: p.curToken,
Operator: p.curToken.Literal,
}
p.nextToken()
expression.Right = p.parseExpression(PREFIX)
return expression
}
var precedences = map[token.TokenType]int{
token.EQ: EQUALS,
token.NOT_EQ: EQUALS,
token.LT: LESSGREATER,
token.GT: LESSGREATER,
token.PLUS: SUM,
token.MINUS: SUM,
token.SLASH: PRODUCT,
token.ASTERISK: PRODUCT,
}
func (p *Parser) peekPrecedence() int {
if p, ok := precedences[p.peekToken.Type]; ok {
return p
}
return LOWEST
}
func (p *Parser) curPrecedence() int {
if p, ok := precedences[p.curToken.Type]; ok {
return p
}
return LOWEST
}
func (p *Parser) nextToken() {
p.curToken = p.peekToken
p.peekToken = p.l.NextToken()
@@ -64,9 +118,6 @@ func (p *Parser) nextToken() {
func (p *Parser) ParseProgram() *ast.Program {
program := &ast.Program{}
program.Statements = []ast.Statement{}
p.prefixParseFns = make(map[token.TokenType]prefixParseFn)
p.registerPrefix(token.IDENT, p.parseIdentifier)
p.registerPrefix(token.INT, p.parseIntegerLiteral)
for p.curToken.Type != token.EOF {
stmt := p.parseStatement()
if stmt != nil {
@@ -137,13 +188,25 @@ func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement {
}
func (p *Parser) parseExpression(precedence int) ast.Expression {
prefix := p.prefixParseFns[p.curToken.Type]
if prefix == nil {
return nil
}
leftExp := prefix()
prefix := p.prefixParseFns[p.curToken.Type]
if prefix == nil {
p.noPrefixParseFnError(p.curToken.Type)
return nil
}
leftExp := prefix()
return leftExp
for !p.peekTokenIs(token.SEMICOLON) && precedence < p.peekPrecedence() {
infix := p.infixParseFns[p.peekToken.Type]
if infix == nil {
return leftExp
}
p.nextToken()
leftExp = infix(leftExp)
}
return leftExp
}
func (p *Parser) parseIntegerLiteral() ast.Expression {
@@ -191,3 +254,22 @@ func (p *Parser) peekError(t token.TokenType) {
func (p *Parser) parseIdentifier() ast.Expression {
return &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
}
func (p *Parser) noPrefixParseFnError(t token.TokenType) {
msg := fmt.Sprintf("no prefix parse function for %s found", t)
p.errors = append(p.errors, msg)
}
func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
expression := &ast.InfixExpression{
Token: p.curToken,
Operator: p.curToken.Literal,
Left: left,
}
precedence := p.curPrecedence()
p.nextToken()
expression.Right = p.parseExpression(precedence)
return expression
}

185
parser/parser_test.go
View File

@@ -4,8 +4,193 @@ import (
"monkey/ast"
"monkey/lexer"
"testing"
"fmt"
)
func TestParsingInfixExpressions(t *testing.T) {
infixTests := []struct {
input string
leftValue int64
operator string
rightValue int64
}{
{"5 + 5;", 5, "+", 5},
{"5 - 5;", 5, "-", 5},
{"5 * 5;", 5, "*", 5},
{"5 / 5;", 5, "/", 5},
{"5 > 5;", 5, ">", 5},
{"5 < 5;", 5, "<", 5},
{"5 == 5;", 5, "==", 5},
{"5 != 5;", 5, "!=", 5},
}
for _, tt := range infixTests {
l := lexer.New(tt.input)
p := New(l)
program := p.ParseProgram()
checkParserErrors(t, p)
if len(program.Statements) != 1 {
t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
1, len(program.Statements))
}
stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
if !ok {
t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
program.Statements[0])
}
exp, ok := stmt.Expression.(*ast.InfixExpression)
if !ok {
t.Fatalf("exp is not ast.InfixExpression. got=%T", stmt.Expression)
}
if !testIntegerLiteral(t, exp.Left, tt.leftValue) {
return
}
if exp.Operator != tt.operator {
t.Fatalf("exp.Operator is not '%s'. got=%s",
tt.operator, exp.Operator)
}
if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
return
}
}
}
func TestOperatorPrecedenceParsing(t *testing.T) {
tests := []struct {
input string
expected string
}{
{
"-a * b",
"((-a) * b)",
},
{
"!-a",
"(!(-a))",
},
{
"a + b + c",
"((a + b) + c)",
},
{
"a + b - c",
"((a + b) - c)",
},
{
"a * b * c",
"((a * b) * c)",
},
{
"a * b / c",
"((a * b) / c)",
},
{
"a + b / c",
"(a + (b / c))",
},
{
"a + b * c + d / e - f",
"(((a + (b * c)) + (d / e)) - f)",
},
{
"3 + 4; -5 * 5",
"(3 + 4)((-5) * 5)",
},
{
"5 > 4 == 3 < 4",
"((5 > 4) == (3 < 4))",
},
{
"5 < 4 != 3 > 4",
"((5 < 4) != (3 > 4))",
},
{
"3 + 4 * 5 == 3 * 1 + 4 * 5",
"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
},
}
for _, tt := range tests {
l := lexer.New(tt.input)
p := New(l)
program := p.ParseProgram()
checkParserErrors(t, p)
actual := program.String()
if actual != tt.expected {
t.Errorf("expected=%q, got=%q", tt.expected, actual)
}
}
}
func TestParsingPrefixExpressions(t *testing.T) {
prefixTests := []struct {
input string
operator string
integerValue int64
}{
{"!5;", "!", 5},
{"-15;", "-", 15},
}
for _, tt := range prefixTests {
l := lexer.New(tt.input)
p := New(l)
program := p.ParseProgram()
checkParserErrors(t, p)
if len(program.Statements) != 1 {
t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
1, len(program.Statements))
}
stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
if !ok {
t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
program.Statements[0])
}
exp, ok := stmt.Expression.(*ast.PrefixExpression)
if !ok {
t.Fatalf("stmt is not ast.PrefixExpression. got=%T", stmt.Expression)
}
if exp.Operator != tt.operator {
t.Fatalf("exp.Operator is not '%s'. got=%s",
tt.operator, exp.Operator)
}
if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
return
}
}
}
func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
integ, ok := il.(*ast.IntegerLiteral)
if !ok {
t.Errorf("il not *ast.IntegerLiteral. got=%T", il)
return false
}
if integ.Value != value {
t.Errorf("integ.Value not %d. got=%d", value, integ.Value)
return false
}
if integ.TokenLiteral() != fmt.Sprintf("%d", value) {
t.Errorf("integ.TokenLiteral not %d. got=%s", value,
integ.TokenLiteral())
return false
}
return true
}
func TestLetStatements(t *testing.T) {
input := `
let x = 5;