Haskell's GHC is a super clever optimizing compiler with a garbage collector built around the sort of memory pressure that arises when you've got tons of immuta

Haskell's GHC is a super clever optimizing compiler with a garbage collector built around the sort of memory pressure that arises when you've got tons of immutable data. Some of GHC's brand of speed comes from the super optimization bits where GHC automatically intuits out a mutating, low level, primitive loop out of your high level description. Some comes from loads and loads of tuning. Clojure cannot benefit from the latter because JVMs are tuned differently and cannot benefit from the first because it has less good transformation semantics.