PR Stanley wrote:
(take 4 . map (>0)) (f s t) where s = 2 : t t = 3 : s f = zipWith (-) What would be the order of evaluation for the above code?
As I understand it Haskell does not specify an order of evaluation and it would therefore be a mistake to write a program which relies on a particular evaluation order. This is the 'unsafe' aspect of unsafePerformIO. It is entirely at the whim of the compiler writer how it is evaluated as long as the eventual answer produced is correct. It would be possible to evaluate it in all sorts of exotic ways, or maybe choose a different one for each day of the week. However, you may be asking how does GHC 6.8.2 evaluate it when compiled at a certain optimisation level so you can make your program run fast or use less memory. In which case there will be a precise answer to your question. Richard.