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parse calls, returns, and expressions

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This commit is contained in:
Chuck Smith
2024-01-18 15:06:46 -05:00
parent fee3e38896
commit 9413094bac
3 changed files with 529 additions and 223 deletions
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261
parser/parser.go
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@@ -17,6 +17,7 @@ const (
PRODUCT // *
PREFIX // -X or !X
CALL // myFunction(X)
INDEX // array[index]
)
var precedences = map[token.TokenType]int{
@@ -28,8 +29,14 @@ var precedences = map[token.TokenType]int{
token.MINUS: SUM,
token.SLASH: PRODUCT,
token.ASTERISK: PRODUCT,
token.LPAREN: CALL,
}
type (
prefixParseFn func() ast.Expression
infixParseFn func(ast.Expression) ast.Expression
)
type Parser struct {
l *lexer.Lexer
errors []string
@@ -41,16 +48,6 @@ type Parser struct {
infixParseFns map[token.TokenType]infixParseFn
}
type (
prefixParseFn func() ast.Expression
infixParseFn func(expression ast.Expression) ast.Expression
)
func (p *Parser) nextToken() {
p.curToken = p.peekToken
p.peekToken = p.l.NextToken()
}
func New(l *lexer.Lexer) *Parser {
p := &Parser{
l: l,
@@ -66,6 +63,7 @@ func New(l *lexer.Lexer) *Parser {
p.registerPrefix(token.FALSE, p.parseBoolean)
p.registerPrefix(token.LPAREN, p.parseGroupedExpression)
p.registerPrefix(token.IF, p.parseIfExpression)
p.registerPrefix(token.FUNCTION, p.parseFunctionLiteral)
p.infixParseFns = make(map[token.TokenType]infixParseFn)
p.registerInfix(token.PLUS, p.parseInfixExpression)
@@ -77,13 +75,53 @@ func New(l *lexer.Lexer) *Parser {
p.registerInfix(token.LT, p.parseInfixExpression)
p.registerInfix(token.GT, p.parseInfixExpression)
// Read two token, so curToken and peekToken are both set
p.registerInfix(token.LPAREN, p.parseCallExpression)
// Read two tokens, so curToken and peekToken are both set
p.nextToken()
p.nextToken()
return p
}
func (p *Parser) nextToken() {
p.curToken = p.peekToken
p.peekToken = p.l.NextToken()
}
func (p *Parser) curTokenIs(t token.TokenType) bool {
return p.curToken.Type == t
}
func (p *Parser) peekTokenIs(t token.TokenType) bool {
return p.peekToken.Type == t
}
func (p *Parser) expectPeek(t token.TokenType) bool {
if p.peekTokenIs(t) {
p.nextToken()
return true
} else {
p.peekError(t)
return false
}
}
func (p *Parser) Errors() []string {
return p.errors
}
func (p *Parser) peekError(t token.TokenType) {
msg := fmt.Sprintf("expected next token to be %s, got %s instead",
t, p.peekToken.Type)
p.errors = append(p.errors, msg)
}
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) ParseProgram() *ast.Program {
program := &ast.Program{}
program.Statements = []ast.Statement{}
@@ -106,7 +144,7 @@ func (p *Parser) parseStatement() ast.Statement {
case token.RETURN:
return p.parseReturnStatement()
default:
return p.parseExpressionsStatement()
return p.parseExpressionStatement()
}
}
@@ -117,65 +155,38 @@ func (p *Parser) parseLetStatement() *ast.LetStatement {
return nil
}
stmt.Name = &ast.Identifier{
Token: p.curToken,
Value: p.curToken.Literal,
}
stmt.Name = &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
if !p.expectPeek(token.ASSIGN) {
return nil
}
// TODO: We're skipping expressions until we
// encounter a semicolon
for !p.curTokenIs(token.SEMICOLON) {
p.nextToken()
stmt.Value = p.parseExpression(LOWEST)
if p.peekTokenIs(token.SEMICOLON) {
p.nextToken()
}
return stmt
}
func (p *Parser) expectPeek(t token.TokenType) bool {
if p.peekTokenIs(t) {
p.nextToken()
return true
} else {
p.peekError(t)
return false
}
}
func (p *Parser) curTokenIs(t token.TokenType) bool {
return p.curToken.Type == t
}
func (p *Parser) peekTokenIs(t token.TokenType) bool {
return p.peekToken.Type == t
}
func (p *Parser) Errors() []string {
return p.errors
}
func (p *Parser) peekError(t token.TokenType) {
msg := fmt.Sprintf("expected next token to be %s, got %s instead", t, p.peekToken.Type)
p.errors = append(p.errors, msg)
}
func (p *Parser) parseReturnStatement() *ast.ReturnStatement {
stmt := &ast.ReturnStatement{Token: p.curToken}
p.nextToken()
// TODO: We're skipping the expression until we encounter a semicolon
for !p.curTokenIs(token.SEMICOLON) {
stmt.ReturnValue = p.parseExpression(LOWEST)
if p.peekTokenIs(token.SEMICOLON) {
p.nextToken()
}
return stmt
}
func (p *Parser) parseExpressionsStatement() *ast.ExpressionStatement {
func (p *Parser) parseExpressionStatement() *ast.ExpressionStatement {
stmt := &ast.ExpressionStatement{Token: p.curToken}
stmt.Expression = p.parseExpression(LOWEST)
@@ -209,6 +220,26 @@ func (p *Parser) parseExpression(precedence int) ast.Expression {
return leftExp
}
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) parseIdentifier() ast.Expression {
return &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
}
func (p *Parser) parseIntegerLiteral() ast.Expression {
lit := &ast.IntegerLiteral{Token: p.curToken}
@@ -224,26 +255,6 @@ func (p *Parser) parseIntegerLiteral() ast.Expression {
return lit
}
func (p *Parser) registerPrefix(tokenType token.TokenType, fn prefixParseFn) {
p.prefixParseFns[tokenType] = fn
}
func (p *Parser) registerInfix(tokenType token.TokenType, fn infixParseFn) {
p.infixParseFns[tokenType] = fn
}
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) parsePrefixExpression() ast.Expression {
expression := &ast.PrefixExpression{
Token: p.curToken,
@@ -257,22 +268,6 @@ func (p *Parser) parsePrefixExpression() ast.Expression {
return expression
}
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) parseInfixExpression(left ast.Expression) ast.Expression {
expression := &ast.InfixExpression{
Token: p.curToken,
@@ -288,10 +283,7 @@ func (p *Parser) parseInfixExpression(left ast.Expression) ast.Expression {
}
func (p *Parser) parseBoolean() ast.Expression {
return &ast.Boolean{
Token: p.curToken,
Value: p.curTokenIs(token.TRUE),
}
return &ast.Boolean{Token: p.curToken, Value: p.curTokenIs(token.TRUE)}
}
func (p *Parser) parseGroupedExpression() ast.Expression {
@@ -299,7 +291,7 @@ func (p *Parser) parseGroupedExpression() ast.Expression {
exp := p.parseExpression(LOWEST)
if p.expectPeek(token.RPAREN) {
if !p.expectPeek(token.RPAREN) {
return nil
}
@@ -324,7 +316,7 @@ func (p *Parser) parseIfExpression() ast.Expression {
return nil
}
expression.Consequence = p.parseBlockExpression()
expression.Consequence = p.parseBlockStatement()
if p.peekTokenIs(token.ELSE) {
p.nextToken()
@@ -333,13 +325,13 @@ func (p *Parser) parseIfExpression() ast.Expression {
return nil
}
expression.Alternative = p.parseBlockExpression()
expression.Alternative = p.parseBlockStatement()
}
return expression
}
func (p *Parser) parseBlockExpression() *ast.BlockStatement {
func (p *Parser) parseBlockStatement() *ast.BlockStatement {
block := &ast.BlockStatement{Token: p.curToken}
block.Statements = []ast.Statement{}
@@ -355,3 +347,86 @@ func (p *Parser) parseBlockExpression() *ast.BlockStatement {
return block
}
func (p *Parser) parseFunctionLiteral() ast.Expression {
lit := &ast.FunctionLiteral{Token: p.curToken}
if !p.expectPeek(token.LPAREN) {
return nil
}
lit.Parameters = p.parseFunctionParameters()
if !p.expectPeek(token.LBRACE) {
return nil
}
lit.Body = p.parseBlockStatement()
return lit
}
func (p *Parser) parseFunctionParameters() []*ast.Identifier {
identifiers := []*ast.Identifier{}
if p.peekTokenIs(token.RPAREN) {
p.nextToken()
return identifiers
}
p.nextToken()
ident := &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
identifiers = append(identifiers, ident)
for p.peekTokenIs(token.COMMA) {
p.nextToken()
p.nextToken()
ident := &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
identifiers = append(identifiers, ident)
}
if !p.expectPeek(token.RPAREN) {
return nil
}
return identifiers
}
func (p *Parser) parseCallExpression(function ast.Expression) ast.Expression {
exp := &ast.CallExpression{Token: p.curToken, Function: function}
exp.Arguments = p.parseExpressionList(token.RPAREN)
return exp
}
func (p *Parser) parseExpressionList(end token.TokenType) []ast.Expression {
list := []ast.Expression{}
if p.peekTokenIs(end) {
p.nextToken()
return list
}
p.nextToken()
list = append(list, p.parseExpression(LOWEST))
for p.peekTokenIs(token.COMMA) {
p.nextToken()
p.nextToken()
list = append(list, p.parseExpression(LOWEST))
}
if !p.expectPeek(end) {
return nil
}
return list
}
func (p *Parser) registerPrefix(tokenType token.TokenType, fn prefixParseFn) {
p.prefixParseFns[tokenType] = fn
}
func (p *Parser) registerInfix(tokenType token.TokenType, fn infixParseFn) {
p.infixParseFns[tokenType] = fn
}