In the last episode we began the journey into exploring the “many faces of zip”. First we played around with the zip that the standard library gives us a bit and saw that it was really useful for coordinating the elements of two sequences in a very safe way so that we don’t have to juggle indices.

Then we zoomed out a bit and looked at the true signature of zip, and we saw that what it was really doing was kinda flipping containers: it transformed a tuple of arrays into an array of tuples.

After that we saw that zip is just a generalization of map: where map allows us to transform a function (A) -> B into a function ([A]) -> [B], zip allowed us to transform a function (A, B) -> C into a function ([A], [B]) -> [C].

This empowered us to define zip on optionals, which is not something that people typically do. It ended up being the perfect solution to a problem that plagued Swift 1: nested if lets! Swift 2 fixed this, but zip still can provide a more ergonomic solution than multiple if lets on the same line.