An idea that clarified itself to me in discussion today is that Swift is to Functional Programming as Java is to Object-Oriented Programming: it is the thing that lets you write C and pretend you’ve adopted some posh-sounding “paradigmatic” non-imperative approach to programming.
I thought this was true shortly before lunch, but now climb partway down from the high horse. Swift is to Functional Programming as Java is to Object-Oriented Programming is still true. However Swift is to C# 3.0 as Java is to Objective-C.
