> You have correctly predicted in advance that the implementation will need to change and can do so without breaking the rest of the application. Some abstract

> You have correctly predicted in advance that the implementation will need to change and can do so without breaking the rest of the application. Some abstractions allow you to avoid predicting things. 'map' is less restrictive than a for-loop if you don't need the powers of a for loop (store state between iterations etc..). So with some abstractions you can postpone restrictions that you don't need and get code that is easier to change. This is probably all obvious but I thought it was important. It can probably be stated more succinctly.