2022-05-26 12:19:15 -05:00
|
|
|
package parser
|
|
|
|
|
|
|
|
import (
|
2022-05-26 14:23:01 -05:00
|
|
|
"fmt"
|
2022-05-26 12:19:15 -05:00
|
|
|
"monkey/ast"
|
|
|
|
"monkey/lexer"
|
|
|
|
"monkey/token"
|
|
|
|
)
|
|
|
|
|
|
|
|
type Parser struct {
|
|
|
|
lexer *lexer.Lexer
|
|
|
|
current_token token.Token
|
|
|
|
peek_token token.Token
|
2022-05-26 14:23:01 -05:00
|
|
|
|
|
|
|
errors []string
|
2022-05-26 12:19:15 -05:00
|
|
|
}
|
|
|
|
|
|
|
|
func New(l_lexer *lexer.Lexer) *Parser {
|
2022-05-26 14:23:01 -05:00
|
|
|
l_parser := &Parser{lexer: l_lexer, errors: []string{}}
|
2022-05-26 12:19:15 -05:00
|
|
|
|
|
|
|
// Read two tokens so current_token and peek_token are both set
|
|
|
|
l_parser.next_token()
|
|
|
|
l_parser.next_token()
|
|
|
|
|
|
|
|
return l_parser
|
|
|
|
}
|
|
|
|
|
2022-05-26 14:23:01 -05:00
|
|
|
func (l_parser *Parser) Errors() []string {
|
|
|
|
return l_parser.errors
|
|
|
|
}
|
|
|
|
|
2022-05-26 12:19:15 -05:00
|
|
|
func (l_parser *Parser) ParseProgram() *ast.Program {
|
|
|
|
program := &ast.Program{}
|
|
|
|
program.Statements = []ast.Statement{}
|
|
|
|
|
2022-05-27 10:07:19 -05:00
|
|
|
for !l_parser.current_token_is(token.EOF) {
|
2022-05-26 12:19:15 -05:00
|
|
|
statement := l_parser.parse_statement()
|
|
|
|
if statement != nil {
|
|
|
|
program.Statements = append(program.Statements, statement)
|
|
|
|
}
|
|
|
|
l_parser.next_token()
|
|
|
|
}
|
|
|
|
return program
|
|
|
|
}
|
|
|
|
|
|
|
|
func (l_parser *Parser) next_token() {
|
|
|
|
l_parser.current_token = l_parser.peek_token
|
|
|
|
l_parser.peek_token = l_parser.lexer.NextToken()
|
|
|
|
}
|
|
|
|
|
|
|
|
func (l_parser *Parser) parse_statement() ast.Statement {
|
|
|
|
switch l_parser.current_token.Type {
|
|
|
|
case token.LET:
|
|
|
|
return l_parser.parse_let_statement()
|
2022-05-27 10:07:19 -05:00
|
|
|
case token.RETURN:
|
|
|
|
return l_parser.parse_return_statement()
|
2022-05-26 12:19:15 -05:00
|
|
|
default:
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
func (l_parser *Parser) parse_let_statement() *ast.LetStatement {
|
|
|
|
statement := &ast.LetStatement{Token: l_parser.current_token}
|
|
|
|
if !l_parser.expect_peek(token.IDENT) {
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
|
|
|
|
statement.Name = &ast.Identifier{Token: l_parser.current_token, Value: l_parser.current_token.Literal}
|
|
|
|
if !l_parser.expect_peek(token.ASSIGN) {
|
|
|
|
return nil
|
|
|
|
}
|
|
|
|
|
|
|
|
// TODO(tijani): Skipping the expressins until there is a semicolon
|
|
|
|
for !l_parser.current_token_is(token.SEMICOLON) {
|
|
|
|
l_parser.next_token()
|
|
|
|
}
|
|
|
|
return statement
|
|
|
|
}
|
|
|
|
|
2022-05-27 10:07:19 -05:00
|
|
|
func (l_parser *Parser) parse_return_statement() *ast.ReturnStatement {
|
|
|
|
statement := &ast.ReturnStatement{Token: l_parser.current_token}
|
|
|
|
l_parser.next_token()
|
|
|
|
|
|
|
|
// TODO(tijani): Skipping the expression until there is semicolon
|
|
|
|
for !l_parser.current_token_is(token.SEMICOLON) {
|
|
|
|
l_parser.next_token()
|
|
|
|
}
|
|
|
|
return statement
|
|
|
|
}
|
|
|
|
|
2022-05-26 12:19:15 -05:00
|
|
|
func (l_parser *Parser) expect_peek(l_token token.TokenType) bool {
|
|
|
|
if l_parser.peek_token_is(l_token) {
|
|
|
|
l_parser.next_token()
|
|
|
|
return true
|
|
|
|
} else {
|
2022-05-26 14:23:01 -05:00
|
|
|
l_parser.peek_error(l_token)
|
2022-05-26 12:19:15 -05:00
|
|
|
return false
|
|
|
|
}
|
|
|
|
}
|
2022-05-26 14:23:01 -05:00
|
|
|
|
|
|
|
func (l_parser *Parser) peek_error(l_token token.TokenType) {
|
|
|
|
message := fmt.Sprintf("expected next token to be %s, got %s", l_token, l_parser.peek_token.Type)
|
|
|
|
l_parser.errors = append(l_parser.errors, message)
|
|
|
|
}
|
|
|
|
|
|
|
|
func (l_parser *Parser) current_token_is(l_token token.TokenType) bool {
|
|
|
|
return l_parser.current_token.Type == l_token
|
|
|
|
}
|
|
|
|
|
|
|
|
func (l_parser *Parser) peek_token_is(l_token token.TokenType) bool {
|
|
|
|
return l_parser.peek_token.Type == l_token
|
|
|
|
}
|