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.VAR):
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 is not None:
body = Stmt.Block([body, Stmt.Expression(increment)])
condition = SyntaxTree.Literal(
True) if condition is None else condition
body = Stmt.While(condition, body)
if initializer is not None:
body = Stmt.Block([initializer, body])
return body
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 Stmt.While(condition, body)
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 Stmt.Var(name, initializer)
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 Stmt.Return(keyword, value)
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 Stmt.If(condition, then_branch, else_branch)
def statement(self):
if self.match(TokenType.FOR):
return self.for_statement()
elif self.match(TokenType.IF):
return self.if_statement()
elif self.match(TokenType.PRINT):
return self.print_statement()
elif self.match(TokenType.RETURN):
return self.return_statement()
elif self.match(TokenType.WHILE):
return self.while_statement()
elif self.match(TokenType.LEFT_BRACE):
return Stmt.Block(self.block())
else:
return self.expression_statement()
def class_declaration(self):
name = self.consume(TokenType.IDENTIFIER, "Expected class name.")
superclass = None
if self.match(TokenType.LESS):
self.consume(TokenType.IDENTIFIER, "Expected superclass name.")
superclass = SyntaxTree.Variable(self.previous())
self.consume(TokenType.LEFT_BRACE, "Expected '{' 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, "Expected '}' after class body.")
return Stmt.Class(name, superclass, methods)
def function(self, kind):
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):
while True:
if len(parameters) >= 255:
self.error(self.peek(),
"Cannot have more than 255 parameters.")
parameters.append(
self.consume(TokenType.IDENTIFIER,
"Expected parameter name."))
if not self.match(TokenType.COMMA):
break
self.consume(TokenType.RIGHT_PAREN, "Expect ')' after parameters.")
self.consume(TokenType.LEFT_BRACE,
"Expect '{' before " + kind + " body.")
body = self.block()
return Stmt.Function(name, parameters, body)
def expression_statement(self):
expression = self.expression()
self.consume(TokenType.SEMICOLON, "Expected ';' after expression.")
return Stmt.Expression(expression)
def print_statement(self):
value = self.expression()
self.consume(TokenType.SEMICOLON, "Expected ';' after value.")
return Stmt.Print(value)