Hi, Recently, Marcin 'Qrczak' Kowalczyk posted a micro-benchmark on comp.lang.functional, illustrating performance with statically typed Int and Integer, and Kogut's dynamically typed automatically-promoted numbers. (Int is fastest, Kogut second, and Integer quite a bit slower). For fun, I tried to use Int64, but to my surprise it is a lot slower than the others. Marcin suggested I look at stg and hc output (which I did without getting much wiser) and made some guesses as to what the reasons were. I'm curious whether this is typical, and if so, whether there is a theoretical reason why Int64 is so slow? (I would have expected a factor of 2-4 worse than Int, but in reality it was about 35x slower) (Code attached, replace MyInt as appropriate.) -kzm -- If I haven't seen further, it is by standing in the footprints of giants