Given a mathematical expression in infix notation, you are required to convert it to postfix notation using the provided code snippet. In postfix notation, operators are written after the operands, whereas in infix notation, operators are written between the operands. Your program should implement a Stack object `stk` and utilize its methods `push(op)`, `push(operand)`, `pop()`, and `display()` to perform the required operations. Your task is to modify the given code snippet by writing the necessary lines of code to convert the infix expression to postfix notation.
user
Sure, I'd be happy to help you modify the given code snippet to perform postfix evaluation. Here's a high-level overview of the steps involved:

1. Create a stack and a string to hold the postfix expression.

2. Traverse through the given infix expression from left to right.

3. If the current character is an operand, append it to the postfix expression.

4. If the current character is an operator, pop the operands (two numerical operands or one numerical operand in case of unary operators) from the stack, perform the operator operation and push the result onto the stack. Append the operator to the postfix expression.

5. Continue to step 2 until no more characters are left in the infix expression.

Here's the Python code implementation of these steps, assuming you have a class `Stack` implementing the stack data structure in Python.

```python
class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if len(self.items) == 0:
            return "Stack is empty"
        return self.items.pop()

    def display(self):
        if len(self.items) == 0:
            print("Stack is empty")
        else:
            print("Stack elements are:", self.items)

    def size(self):
        return len(self.items)


infix = "23+4*5-6"
postfix = ""
stack = Stack()

i = 0
while I < len(infix):
    ch = infix[i]
    if ch.isdigit():
        postfix += ch
    elif ch in "+-*":
        a = stack.pop()
        b = stack.pop()

        if ch == '+':
            result = int(b) + int(a)
        elif ch == '-':
            result = int(b) - int(a)
        elif ch == '*':
            result = int(b) * int(a)

        postfix += ch
        stack.push(result)
    I += 1

print("Postfix expression", postfix)
print("Stack elements are:", stack.items)
```

This code snippet assumes that the infix expression is a string with numbers and operators. If you have a more complex infix expression, you may need to modify this code according to its syntax.
assistant
Given a mathematical expression in infix notation, you are required to convert it to postfix notation using the provided code snippet. In postfix notation, operators are written after the operands, whereas in infix notation, operators are written between the operands. Your program should implement a Stack object `stk` and utilize its methods `push(op)`, `push(operand)`, `pop()`, and `display()` to perform the required operations. Your task is to modify the given code snippet by writing the necessary lines of code to convert the infix expression to postfix notation.
user
Sure, I can help you with that. Here's a Python code snippet that converts an infix expression to a postfix expression using a stack:

```python
class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        return self.items.pop()

    def is_empty(self):
        return len(self.items) == 0

    def display(self):
        print(self.items)

def precedence(op):
    if op == '+' or op == '-':
        return 1
    if op == '*' or op == '/':
        return 2
    return 0

def infix_to_postfix(infix_exp):
    postfix_exp = ""
    stk = Stack()

    for token in infix_exp:
        if token.isalnum():
            postfix_exp += token
        elif token == '(':
            stk.push(token)
        elif token == ')':
            while not stk.is_empty() and stk.items[-1] != '(':
                postfix_exp += stk.pop()
            stk.pop()
        else:  # operator
            while not stk.is_empty() and precedence(stk.items[-1]) >= precedence(token):
                postfix_exp += stk.pop()
            stk.push(token)

    while not stk.is_empty():
        postfix_exp += stk.pop()

    return postfix_exp

# Test the function
infix_exp = "a+(b*(c-(d/e))"
print("Infix expression: ", infix_exp)
print("Postfix expression: ", infix_to_postfix(infix_exp))
```

This code first defines a `Stack` class with methods for pushing, popping, checking if it's empty, and displaying its contents. The `precedence` function returns the precedence of an operator. The `infix_to_postfix` function converts an infix expression to a postfix expression. It iterates over each token in the infix expression. If the token is an operand (i.e., a letter or a number), it adds it to the postfix expression. If the token is a left parenthesis, it pushes it to the stack. If the token is a right parenthesis, it pops from the stack until it encounters a left parenthesis. If the token is an operator, it pops operators from the stack that have equal or higher precedence and adds them to the postfix expression, then pushes the operator to the stack. Finally, it pops any remaining operators from the stack and adds them to the postfix expression.
assistant