infix_to_postfix_with_tests

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Filename: infix_to_postfix_with_tests.py
# Version: 1.0.0
# Author: Jeoi Reqi

"""
Description:
    - This script converts infix expressions to postfix expressions.
    - It features an interactive menu that allows users to input their own infix expressions for conversion.
    - Additionally, users can run a series of predefined test cases to verify the accuracy of the conversion function.

Functions:
    - infix_to_postfix(infix_expression):
      Converts an infix expression to a postfix expression.
    - run_tests():
      Runs a set of predefined test cases to verify the correctness of the conversion function.
    - main():
      Provides an interactive menu for the user to choose between entering their own infix expression or running predefined test cases.

Requirements:
    - Python 3.x

Usage:
    1. Run the script: python infix_to_postfix_with_tests.py
    2. Follow the menu prompts:
        - Choose option 1 to enter your own infix expression and get the postfix result.
        - Choose option 2 to run predefined test cases and see the results.
        - Choose option 3 to exit the script.

Additional Notes:
    - The script handles basic arithmetic operators (+, -, *, /, ^) and parentheses.
    - It includes error handling for mismatched parentheses in the input expression.
    - The predefined test cases cover various scenarios to ensure the function works correctly.
"""

def infix_to_postfix(infix_expression):
    """
    Convert an infix expression to a postfix expression.

    Params:
        infix_expression (str): Infix expression provided by the user.

    Returns:
        str: Postfix expression converted from the infix one.
    """
    stack = []
    postfix_expression = ""
    for char in infix_expression:
        if char.isalnum():  # If an operand, add to postfix expression
            postfix_expression += char
        elif char == '(':
            stack.append(char)
        elif char == ')':
            while stack and stack[-1] != '(':
                postfix_expression += stack.pop()
            if not stack:
                raise ValueError("\nMismatched parentheses!\n")
            stack.pop()
        else:
            while stack and stack[-1] != '(' and priorities[char] <= priorities[stack[-1]]:
                postfix_expression += stack.pop()
            stack.append(char)

    while stack:
        top = stack.pop()
        if top == '(' or top == ')':
            raise ValueError("\nMismatched parentheses!\n")
        postfix_expression += top

    return postfix_expression

# Set of operators and their priorities
operators = set(["+", "-", "*", "/", "(", ")", "^"])
priorities = {"+": 1, "-": 1, "*": 2, "/": 2, "^": 3}

# Function to run test cases (Option 2)
def run_tests():
    """
    Run a series of predefined test cases to verify the correctness of the infix_to_postfix function.
    """
    test_cases = [
        ("A+B", "AB+"),
        ("A+B*C", "ABC*+"),
        ("(A+B)*C", "AB+C*"),
        ("A+B*(C^D-E)", "ABCD^E-*+"),
        ("A+B-C", "AB+C-"),
        ("((A+B)*C-(D-E))^(F+G)", "AB+C*DE--FG+^"),
        ("A", "A"),
        ("(A+B)*(C+D)", "AB+CD+*")
    ]

    print("\nRunning test cases...\n")
    for i, (infix, expected_postfix) in enumerate(test_cases):
        try:
            result = infix_to_postfix(infix)
            assert result == expected_postfix, f"Test case {i+1} failed: expected {expected_postfix}, got {result}"
            print(f"Test case {i+1} passed: {infix} -> {result}")
        except AssertionError as e:
            print(e)
    print("\nAll test cases completed.\n")

def main():
    """
    Main function to provide an interactive menu for the user.
    Allows the user to enter their own infix expression or run predefined test cases.
    """
    while True:
        print("\nOptions Menu:\n")
        print("1. Enter your own infix expression")
        print("2. Run predefined test cases")
        print("3. Exit")
        choice = input("\nChoose an option (1/2/3): ")

        if choice == '1':
            infix_expression = input("\nEnter infix expression: ").replace(" ", "")
            try:
                postfix_expression = infix_to_postfix(infix_expression)
                print("\nPostfix expression:", postfix_expression)
            except ValueError as ve:
                print("\nError:", ve)
        elif choice == '2':
            run_tests()
        elif choice == '3':
            break
        else:
            print("\nInvalid choice! Please choose again.\n")

if __name__ == "__main__":
    main()