For this tutorial we'll be using a simplified version of our expression tree. Our expressions accept only binary expressions that combine Integers and Strings using plus and minus operators. The rules are simple:
- Adding or subtracting two integers is allowed. The result is the sum/subtraction of both numbers
- Adding two strings or a string and an integer is allowed. The result will be the result of concatenating both operands as if they were strings
- Subtracting a String from an int (or vice versa) is not allowed