"While >>= and return are the basic monadic sequencing operations, we also need some monadic primitives. A monadic primitive is simply an operation that uses the insides of the monad abstraction and taps into the `wheels and gears' that make the monad work. For example, in the IO monad, operators such as putChar are primitive since they deal with the inner workings of the IO monad. Similarly, our state monad uses two primitives: readSM and updateSM. Note that these depend on the inner structure of the monad..."

Or, possibly because when I make a post on Hacker News about how difficult it is to implement Quicksort in Haskell, the first response is a four-line Haskell implementation of Quicksort, spawning a 50-post subthread which points out that it's not actually an implementation of Quicksort, because it does not have the same performance characteristics as Quicksort, and instead has the performance characteristics of a lethargic water buffalo.

By the end of the thread, the question of whether it is possible to write a Quicksort in Haskell that has the performance characteristics of Quicksort is left as an open research question.