Implement a postfix calculator in C++

Question Description

The postfix calculator application:

1. Write a postfix calculator application in C++.
2. The only operators you need to implement are '+', '-', '*', and '/'. However, your implementation should make it relatively easy to add more operators, such as 'pow', 'sqrt' or etc. Feel free to implement these additional operators should you feel adventurous.
3. The calculator should accept floating point numbers and output floating point numbers (i.e. when the input is 2 3 / the result is 0.66667).
4. The calculator will read a postfix expression contained in a single line from stdin and output the result to stdout.
5. You can use a different container to implement it instead of using a stack and be able to explain why.
6. After each evaluation, the calculator must prompt for another expression, continuing until the user enters the text “exit” (without the quotes).
7. The calculator must output an error message if the expression contains an error. For example, characters like a or ? or ~ will generate error messages. Invalid postfix expressions must also generate error messages. For example, the expression 2 + 3 is not a valid postfix expression. There are four types of error messages:

• "Invalid operand"
• "Invalid operator"
• "Too many operands"
• "Not enough operands"
  Note: Your application will need to return these exact strings to pass some of the test cases.

1. A testing methodology should be considered. You do not necessarily need to write tests, but you should be able to talk about how you would test.
2. You may consult the web for library reference only, but copying a solution from websites or LLM (e.g. ChatGPT, Claude, etc) will be recognized, especially since none of them are particularly good.

Basic Algorithm:

For each token 'ch' in the postfix expression, do:

• if 'ch' is an operator op, then

1. a := pop first element from stack
2. b := pop second element from the stack
3. res := op(b, a)
4. push res into the stack

• else if 'ch' is an operand, then

1. add ch into the stack

Provided Test Cases:

The test cases given below are not comprehensive, but rather represent a small sample to illustrate the expected functionality.

Input	Expected Output
2 3 /	0.666667
2.0 6 -	-4
200.0 -5.0 *	-1000
error	Invalid operator
100 3 4 + 1	Too many operands

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