Haskell may potentially be compiled to within epsilon of C when using strict evaluation + mutable state + unboxed types (look at the shootout implementations; t

Haskell may potentially be compiled to within epsilon of C when using strict evaluation + mutable state + unboxed types (look at the shootout implementations; the majority are in this style), but lazy evaluation and functional data structures have a real cost. It's not merely that the ghc developers have been insufficiently clever and diligent.