92 lines
1.6 KiB
Go
92 lines
1.6 KiB
Go
package parser
|
|
|
|
import (
|
|
"monkey/ast"
|
|
"monkey/lexer"
|
|
"monkey/token"
|
|
)
|
|
|
|
type Parser struct {
|
|
l *lexer.Lexer
|
|
|
|
curToken token.Token
|
|
peekToken token.Token
|
|
}
|
|
|
|
func New(l *lexer.Lexer) *Parser {
|
|
p := &Parser{l: l}
|
|
|
|
// 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) ParseProgram() *ast.Program {
|
|
program := &ast.Program{}
|
|
program.Statements = []ast.Statement{}
|
|
|
|
for p.curToken.Type != token.EOF {
|
|
stmt := p.parseStatement()
|
|
if stmt != nil {
|
|
program.Statements = append(program.Statements, stmt)
|
|
}
|
|
p.nextToken()
|
|
}
|
|
|
|
return program
|
|
}
|
|
func (p *Parser) parseStatement() ast.Statement {
|
|
switch p.curToken.Type {
|
|
case token.LET:
|
|
return p.parseLetStatement()
|
|
default:
|
|
return nil
|
|
}
|
|
}
|
|
|
|
func (p *Parser) parseLetStatement() *ast.LetStatement {
|
|
stmt := &ast.LetStatement{Token: p.curToken}
|
|
|
|
if !p.expectPeek(token.IDENT) {
|
|
return nil
|
|
}
|
|
|
|
stmt.Name = &ast.Identifier{Token: p.curToken, Value: p.curToken.Literal}
|
|
|
|
if !p.expectPeek(token.ASSIGN) {
|
|
return nil
|
|
}
|
|
|
|
// TODO: We're skipping the expressions until we
|
|
// encounter a semicolon
|
|
for !p.curTokenIs(token.SEMICOLON) {
|
|
p.nextToken()
|
|
}
|
|
|
|
return stmt
|
|
}
|
|
|
|
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 {
|
|
return false
|
|
}
|
|
}
|