RE HAMTs that's sort of true. Transients are a real leap forward that the FP community didn't have before (things like Haskell's ST generally require at least o

RE HAMTs that's sort of true. Transients are a real leap forward that the FP community didn't have before (things like Haskell's ST generally require at least one full copy of an immutable data structure into a mutable one). Clojure's choice of dedicated syntax for each of its main data structures is also an interesting ergonomic choice (which sadly few languages have chosen to copy). However the presence of a commonly available vector-like data structure (a data structure with logarithmic or better cons, snoc, and indexing) is not new. For example Haskell's vector-like Data.Sequence predates Clojure (as does its Patrica Trie and Map implementations). RE higher-order functions I was being imprecise. I meant user-defined higher order functions. It's very common to use higher order functions, but it's rather uncommon to define your own new ones. Incidentally, I think Clojure transducers are one instance where they've used a higher order function when a first order function would do. It turns out that transducers can be implemented as functions of the form `a -> List b` rather than the usual presentation as a higher order function on reducers. Yes even though there's a List it works on non-collection things.