107 lines
1.8 KiB
Go
107 lines
1.8 KiB
Go
package parser
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import (
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"fmt"
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"gitlab.com/Tyrel/monkey/ast"
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"gitlab.com/Tyrel/monkey/lexer"
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"gitlab.com/Tyrel/monkey/token"
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)
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type Parser struct {
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l *lexer.Lexer
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curToken token.Token
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peekToken token.Token
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errors []string
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}
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func New(l *lexer.Lexer) *Parser {
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p := &Parser{
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l: l,
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errors: []string{},
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}
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// get two tokens to curToken and peekToken are set
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p.nextToken()
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p.nextToken()
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return p
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}
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func (p *Parser) Errors() []string {
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return p.errors
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}
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func (p *Parser) nextToken() {
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p.curToken = p.peekToken
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p.peekToken = p.l.NextToken()
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}
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func (p *Parser) ParseProgram() *ast.Program {
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program := &ast.Program{}
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program.Statements = []ast.Statement{}
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for p.curToken.Type != token.EOF {
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stmt := p.parseStatement()
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if stmt != nil {
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program.Statements = append(program.Statements, stmt)
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}
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p.nextToken()
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}
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return program
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}
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func (p *Parser) parseStatement() ast.Statement {
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switch p.curToken.Type {
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case token.LET:
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return p.parseLetStatement()
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default:
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return nil
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}
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}
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func (p *Parser) parseLetStatement() *ast.LetStatement {
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stmt := &ast.LetStatement{Token: p.curToken}
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if !p.expectPeek(token.IDENT) {
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return nil
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}
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stmt.Name = &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
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if !p.expectPeek(token.ASSIGN) {
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return nil
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}
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for !p.curTokenIs(token.SEMICOLON) {
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p.nextToken()
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}
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return stmt
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}
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func (p *Parser) curTokenIs(t token.TokenType) bool {
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return p.curToken.Type == t
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}
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func (p *Parser) peekTokenIs(t token.TokenType) bool {
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return p.peekToken.Type == t
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}
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func (p *Parser) expectPeek(t token.TokenType) bool {
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if p.peekTokenIs(t) {
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p.nextToken()
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return true
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} else {
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p.peekError(t)
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return false
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}
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}
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func (p *Parser) peekError(t token.TokenType) {
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msg := fmt.Sprintf("expected next token to be %s. got=%s", t, p.peekToken.Type)
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p.errors = append(p.errors, msg)
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}
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