In completing exercise 4 of Taking a Vacation, an expression was used that seems on the surface to be functionally identical to what I initially used. My first effort attempted to use this syntax:
a == a - x
The correct answer used this syntax:
a -= x
What is the functional difference between the way these are processed? Why would the first not provide the correct answer, while the second does? As far as I have learned so far, they do the same thing, don't they?