On Fri, Feb 6, 2009 at 1:00 PM, Antoine Latter
Tangential to all of this - sometimes my unsafeXXX functions are pure, but partial. So I'll have:
foo :: a -> b -> Maybe c
and
unsafeFoo :: a -> b -> c
I use the "unsafe" prefix in the same way. For me it means 'assume that preconditions hold'. If the preconditions do not hold and you evaluate an unsafe function anyway I would expect an error, as opposed to an exception. I have done that in my (tiny) roman numerals package. -- simplified toRoman :: Int -> Either String Int unsafeToRoman :: Int -> String The first function is very clear about the fact that something can go wrong. If you provide it with a value of (-3) it will (hopefully) produce something like 'Left "no negative numbers allowed"'. The second function hides this fact and will result in a (uncatchable) runtime error. It is still a pure function, but preventing errors is now the responsibility of whoever evaluates it.