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parser_.py
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parser_.py
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from native import StringInstance
from hoot import Hoot
from typing import List
from error import ParseError
from tokens import Token, TokenType
from expr import Assign, Binary, Call, Get, Grouping, Letiable, Literal, Logical, Set, Super, This, Unary
from stmt import Block, Break, Class, Expression, Function, If, Let, Print, Return, While
class Parser:
def __init__(self, hoot: Hoot, tokens: List[Token]):
self.hoot = hoot
self.current = 0
self.tokens = tokens
self._lambda = 0
return
def parse(self):
statements = []
while not self.is_at_end():
statements.append(self.declaration())
return statements
def expression(self):
return self.assignment()
def declaration(self):
try:
if self.match([TokenType.CLASS]):
return self.class_declaration()
if self.match([TokenType.FUN]):
return self.function("function")
if self.match([TokenType.LET]):
return self.var_declaration()
return self.statement()
except ParseError:
self.synchronize()
def class_declaration(self):
name = self.consume(TokenType.IDENTIFIER, "Expect class name.")
superclass = None
if self.match([TokenType.LESS]):
self.consume(TokenType.IDENTIFIER, "Expect superclass name")
superclass = Letiable(self.previous())
self.consume(TokenType.LEFT_BRACE, "Expect '{' before class body.")
methods = []
while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
methods.append(self.function("method"))
self.consume(TokenType.RIGHT_BRACE, "Expect '}' after class body.")
return Class(name, superclass, methods)
def statement(self):
if self.match([TokenType.FOR]):
return self.for_statement()
if self.match([TokenType.IF]):
return self.if_statement()
if self.match([TokenType.PRINT]):
return self.print_statement()
if self.match([TokenType.RETURN]):
return self.return_statement()
if self.match([TokenType.WHILE]):
return self.while_statement()
if self.match([TokenType.BREAK]):
return self.break_statement()
if self.match([TokenType.LEFT_BRACE]):
return Block(self.block())
return self.expression_statement()
def for_statement(self):
self.consume(TokenType.LEFT_PAREN, "Expect '(' after 'for'.")
initializer = None
if self.match([TokenType.SEMICOLON]):
initializer = None
elif self.match([TokenType.LET]):
initializer = self.var_declaration()
else:
initializer = self.expression_statement()
condition = None
if not self.check(TokenType.SEMICOLON):
condition = self.expression()
self.consume(TokenType.SEMICOLON, "Expect ';' after loop condition.")
increment = None
if not self.check(TokenType.RIGHT_PAREN):
increment = self.expression()
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after for clauses.")
body = self.statement()
if increment != None:
body = Block([
body,
Expression(increment),
])
if condition == None:
condition = Literal(True)
body = While(condition, body)
if initializer != None:
body = Block([
initializer,
body,
])
return body
def if_statement(self):
self.consume(TokenType.LEFT_PAREN, "Expect '(' after 'if'.")
condition = self.expression()
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after if condition.")
then_branch = self.statement()
else_branch = None
if self.match([TokenType.ELSE]):
else_branch = self.statement()
return If(condition, then_branch, else_branch)
def print_statement(self):
value = self.expression()
self.consume(TokenType.SEMICOLON, "Expect ';' after value.")
return Print(value)
def return_statement(self):
keyword = self.previous()
value = None
if not self.check(TokenType.SEMICOLON):
value = self.expression()
self.consume(TokenType.SEMICOLON, "Expect ';' after return value.")
return Return(keyword, value)
def var_declaration(self):
name = self.consume(TokenType.IDENTIFIER, "Expect variable name.")
initializer = None
if self.match([TokenType.EQUAL]):
initializer = self.expression()
self.consume(TokenType.SEMICOLON,
"Expect ';' after variable declaration.")
return Let(name, initializer)
def while_statement(self):
self.consume(TokenType.LEFT_PAREN, "Expect '(' after 'while'.")
condition = self.expression()
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after condition.")
body = self.statement()
return While(condition, body)
def break_statement(self):
self.consume(TokenType.SEMICOLON,
"Expect ';' after 'break' statement.")
return Break()
def expression_statement(self):
value = self.expression()
self.consume(TokenType.SEMICOLON, "Expect ';' after expression.")
return Expression(value)
def function(self, kind: str):
name = self.consume(TokenType.IDENTIFIER, f"Expect '{kind}' name.")
self.consume(TokenType.LEFT_PAREN, f"Expect '(' after {kind} name.")
parameters = []
if not self.check(TokenType.RIGHT_PAREN):
parameters.append(self.consume(
TokenType.IDENTIFIER, "Expect parameter name."))
while self.match([TokenType.COMMA]):
# https://craftinginterpreters.com/functions.html#maximum-argument-counts
if len(parameters) >= 255:
self.error(
self.peek(), "Can't have more than 255 parameters.")
parameters.append(self.consume(
TokenType.IDENTIFIER, "Expect parameter name."))
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after parameters.")
self.consume(TokenType.LEFT_BRACE, f"Expect '}}' before {kind} body.")
body = self.block()
return Function(name, parameters, body)
def block(self):
statements = []
while not self.check(TokenType.RIGHT_BRACE) and not self.is_at_end():
statements.append(self.declaration())
self.consume(TokenType.RIGHT_BRACE, "Expect '}' after block.")
return statements
def assignment(self):
expr = self.or_()
if self.match([TokenType.EQUAL]):
equals = self.previous()
value = self.assignment()
if type(expr) == Letiable:
name = expr.name
return Assign(name, value)
if type(expr) == Get:
get = expr
return Set(get.obj, get.name, value)
self.error(equals, "Invalid assignment target.")
return expr
def or_(self):
expr = self.and_()
while self.match([TokenType.OR]):
operator = self.previous()
right = self.and_()
expr = Logical(expr, operator, right)
return expr
def and_(self):
expr = self.equality()
while self.match([TokenType.AND]):
operator = self.previous()
right = self.equality()
expr = Logical(expr, operator, right)
return expr
def equality(self):
expr = self.comparison()
while self.match([TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL]):
operator = self.previous()
right = self.comparison()
expr = Binary(expr, operator, right)
return expr
def comparison(self):
expr = self.term()
while self.match([TokenType.GREATER, TokenType.GREATER_EQUAL, TokenType.LESS, TokenType.LESS_EQUAL]):
operator = self.previous()
right = self.term()
expr = Binary(expr, operator, right)
return expr
def term(self):
expr = self.factor()
while self.match([TokenType.MINUS, TokenType.PLUS]):
operator = self.previous()
right = self.factor()
expr = Binary(expr, operator, right)
return expr
def factor(self):
expr = self.unary()
while self.match([TokenType.SLASH, TokenType.STAR]):
operator = self.previous()
right = self.unary()
expr = Binary(expr, operator, right)
return expr
def unary(self):
if self.match([TokenType.BANG, TokenType.MINUS]):
operator = self.previous()
right = self.unary()
return Unary(operator, right)
return self.call()
def finish_call(self, callee):
arguments = []
if not self.check(TokenType.RIGHT_PAREN):
arguments.append(self.expression())
while self.match([TokenType.COMMA]):
# https://craftinginterpreters.com/functions.html#maximum-argument-counts
if len(arguments) >= 255:
self.error(
self.peek(), "Can't have more than 255 arguments.")
arguments.append(self.expression())
paren = self.consume(TokenType.RIGHT_PAREN,
"Expect ')' after arguments.")
return Call(callee, paren, arguments)
def call(self):
expr = self.primary()
while True:
if self.match([TokenType.LEFT_PAREN]):
expr = self.finish_call(expr)
elif self.match([TokenType.DOT]):
name = self.consume(TokenType.IDENTIFIER,
"Expect property name after '.'.")
expr = Get(expr, name)
else:
break
return expr
def primary(self):
if self.match([TokenType.FALSE]):
return Literal(False)
if self.match([TokenType.TRUE]):
return Literal(True)
if self.match([TokenType.NIL]):
return Literal(None)
if self.match([TokenType.NUMBER, TokenType.STRING]):
return Literal(self.previous().literal)
if self.match([TokenType.SUPER]):
keyword = self.previous()
self.consume(TokenType.DOT, "Expect '.' after 'super'.")
method = self.consume(TokenType.IDENTIFIER,
"Expect superclass method name.")
return Super(keyword, method)
if self.match([TokenType.THIS]):
return This(self.previous())
if self.match([TokenType.IDENTIFIER]):
return Letiable(self.previous())
if self.match([TokenType.LEFT_PAREN]):
expr = self.expression()
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after expression.")
return Grouping(expr)
raise self.error(self.peek(), "Expect expression.")
def consume(self, type_: TokenType, message: str):
if self.check(type_):
return self.advance()
raise self.error(self.peek(), message)
def match(self, types: List[TokenType]):
for type_ in types:
if self.check(type_):
self.advance()
return True
return False
def check(self, type_: TokenType):
if self.is_at_end():
return False
return self.peek().type_ == type_
def advance(self):
if not self.is_at_end():
self.current += 1
return self.previous()
def is_at_end(self):
return self.peek().type_ == TokenType.EOF
def peek(self):
return self.tokens[self.current]
def previous(self):
return self.tokens[self.current-1]
def error(self, token: Token, message: str):
self.hoot.error(token, message)
return ParseError(f'{token} {message}')
def synchronize(self):
self.advance()
while not self.is_at_end():
if self.previous().type_ == TokenType.SEMICOLON:
return
if self.peek() in [
TokenType.CLASS,
TokenType.FUN,
TokenType.LET,
TokenType.FOR,
TokenType.IF,
TokenType.WHILE,
TokenType.BREAK,
TokenType.PRINT,
TokenType.RETURN,
]:
return
self.advance()