def infix_to_postfix(expression):
operator_stack = Stack()
output = []
token_list = expression.split()
precedence = {"^": 4, "*": 3, "/": 3, "+": 2, "-": 2, "(": 1}
chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
for token in token_list:
try:
int(token)
number = True
except ValueError:
number = False
if token in chars or number:
output.append(token)
elif token == "(":
operator_stack.add(token)
elif token == ")":
stack_token = operator_stack.pop()
while stack_token != "(":
output.append(stack_token)
stack_token = operator_stack.pop()
else:
while (not operator_stack.is_empty()) and \
(precedence[operator_stack.peek()] >= precedence[token]):
output.append(operator_stack.pop())
operator_stack.add(token)
while not operator_stack.is_empty():
output.append(operator_stack.pop())
return " ".join(output)
class StackQueue:
def __init__(self):
self._stack1 = Stack()
self._stack2 = Stack()
self._loaded = True
def enqueue(self, value):
if not self._loaded:
self._reload()
self._stack1.push(value)
def dequeue(self):
if not self._loaded:
return self._stack2.pop()
self._unload()
return self._stack1.pop()
def peek(self):
self._unload()
value = self._stack1.peek()
self._reload()
return value
def count(self):
return self._stack1.count if self._loaded else self._stack2.count
def _unload(self):
while self._stack1.count > 1:
self._stack2.push(self._stack1.pop())
self._loaded = False
def _reload(self):
while self._stack2.count > 0:
self._stack1.push(self._stack2.pop())
self._loaded = True
def infixToPostfix(tokenList):
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
prec[">"] = 0
prec["<"] = 0
prec["="] = 0
prec[">="] = 0
prec["<="] = 0
opStack = Stack()
postfixList = []
for token in tokenList:
if token.isnumeric() or token not in [
'+', '-', '*', '/', '(', ')', '>', '<', '=', '<=', '>='
]:
if not token.isnumeric():
token = tabela_sintatica.tabela[token]['value']
if not token.isnumeric():
print("erro! variável sem valor atribuído." + token)
exit()
postfixList.append(token)
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != '(':
postfixList.append(topToken)
topToken = opStack.pop()
else:
while (not opStack.isEmpty()) and \
(prec[opStack.peek()] >= prec[token]):
postfixList.append(opStack.pop())
opStack.push(token)
while not opStack.isEmpty():
postfixList.append(opStack.pop())
return postfixList