Where does the “flatmap that s***” idiomatic expression in Scala come from?

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The story I heard was that two preeminent Scala programmers were pairing when one of them started writing some code like this:

option match {
    case Some ...

At which point the other said “What is this? Amateur hour? Flat map that shit!”

As to what’s so powerful about flatMap, well… First, it’s the fundamental monadic operator. That means it is a common operation shared by, for example, containers (such as Option, collections, etc), continuations, state, etc. Second, while you can de-construct an Option, that, as opposed to flatMap, is not a monadic operation, so it cannot be as widely applied. Also, it requires too much knowledge about the data you are manipulating.

Note: previously I said matching was slower than flatMap — the opposite is true as a matter of fact, up to the most recent version of Scala at the time of this writing, 2.10.1.)

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