def term(self):
"""Match the grammar for a term."""
self.stack.append("Factor")
operator_map = {"*": "*", "DIV": "/", "MOD": "%"}
cur = self.factor()
# 0 or more patterns.
while True:
if self.current.kind == "*" or self.current.kind == "DIV" or self.current.kind == "MOD":
if self.current.kind == "*":
operator = self.match("*")
elif self.current.kind == "DIV":
operator = self.match("DIV")
else:
operator = self.match("MOD")
self.stack.append("Factor")
var = self.factor()
if isinstance(cur, Number) and isinstance(var, Number):
# Constant folding.
try:
val = int(eval(str(cur.entry.value) + str(operator_map[operator.kind]) + str(var.entry.value)))
except ZeroDivisionError:
# Divide by 0 error.
self.invalid_token(DivideByZero(self.last))
break
const = Constant(self.integer_type, val)
cur = Number(const)
else:
if isinstance(cur, VariableAST) and (
isinstance(cur.variable, Array) or isinstance(cur.variable, Record)
):
# Trying to perform an operation on non-integers.
try:
raise InvalidArithmeticOperation(cur, self.last)
except InvalidArithmeticOperation as e:
self.invalid_token(e)
else:
cur = Binary(operator.kind, cur, var, self.integer_type)
# Remember the token for node in case of run time errors.
cur.token = self.last
else:
# Pattern ended.
break
return cur
def expression(self):
"""Match the grammar of an expression."""
operator = None
if self.current.kind == "+":
operator = self.match("+")
elif self.current.kind == "-":
operator = self.match("-")
self.stack.append("Term")
cur = self.term()
if operator != None and operator.kind == "-":
# Negate the expression if needed.
if isinstance(cur, Number):
# Constant folding.
cur = Number(Constant(self.integer_type, eval(str(operator.kind) + str(cur.entry.value))))
else:
if isinstance(cur, VariableAST) and (
isinstance(cur.variable, Array) or isinstance(cur.variable, Record)
):
# Trying to perform an operation on non-integers.
try:
raise InvalidArithmeticOperation(cur, self.last)
except InvalidArithmeticOperation as e:
self.invalid_token(e)
else:
cur = Binary(operator.kind, Number(Constant(self.integer_type, 0)), cur, self.integer_type)
# Remember the token for node in case of run time errors.
cur.token = self.last
# 0 or more patterns.
while True:
if self.current.kind in {"+", "-"}:
if self.current.kind == "+":
operator = self.match("+")
else:
operator = self.match("-")
self.stack.append("Term")
var = self.term()
if isinstance(cur, Number) and isinstance(var, Number):
# Constant folding.
cur = Number(
Constant(
self.integer_type, eval(str(cur.entry.value) + str(operator.kind) + str(var.entry.value))
)
)
else:
if isinstance(cur, VariableAST) and (
isinstance(cur.variable, Array) or isinstance(cur.variable, Record)
):
# Trying to perform an operation on non-integers.
try:
raise InvalidArithmeticOperation(cur, self.last)
except InvalidArithmeticOperation as e:
self.invalid_token(e)
else:
cur = Binary(operator.kind, cur, var, self.integer_type)
# Remember token for node in case of run time errors.
cur.token = self.last
else:
# Pattern ended.
break
if cur == None:
# Return an invalid variable node in case of parsing errors.
cur = VariableAST("INVALID", Variable(Invalid()))
return cur