Write a program that converts infix expressions to postfix expressions. This program should use the Token and Scanner classes developed in the case study of this chapter.

A portion of the convert() method has been provided, but must be completed for the method to successfully convert the infix expression to postfix.

Be sure to reuse your solution from Programming Exercise 7.4 as your starter file for the scanner.py and tokens.py files.

In the Token class of the tokens.py file, complete the following:

1. Define the getPrecedence() method.
   • Returns an integer that represents the precedence level of an operator.
     • If the token contains the exponential operator (EXPO), return 3
     • If the token contains the multiply (MUL) or the divide operator (DIV), return 2
     • If the token contains the addition (PLUS) or the subtraction operator (MINUS), return 1

In the IFToPFConverter class of the converter.py file, complete the following:

1. Complete the implementation of the convert() method.
   • This method returns a list of tokens that represents the postfix string (Assumes that the infix expression is syntactically correct).
   • When the stack is not empty and the precedence is greater or equal to the currentToken precedence:
     • Append the stack to postfix
   • If the stack stack.isEmpty() is empty and the exponential operator Token.EXPO is not the current token:
     • Push the currentToken to the stack
2. Complete the implementation of the main() method that performs the inputs and outputs.
   • The main() method receives an input string and creates a scanner with it.
   • The scanner is then passed as an argument to the constructor of the converter object.
   • The converter objects convert() method is then run to convert the infix expression using the algorithm described in this chapter.
   • The main() method then displays this string.

Note: You should assume for this project that the user always enters a syntactically correct infix expression.

To test your program run the main() method in the converter.py file.