[Haskell-cafe] GHCi Loop Detection

Hi Cafe, Is there a reason that the GHCi interpreter doesn't detect and report infinite loops in statements like this (like compiled programs do) even though no CPU time appears to be used? My (admittedly weak) searching for an answer didn't turn much up. let s | not $ null s = [] in s GHCi v7.0.4 on OSX Thanks, John