On Jan 9, 2008 5:42 PM, Henning Thielemann
I just want to point out that unsafePerformIO is at the core of the (safe) bytestring library. As SPJ et al pointed out, this is crucial functionality, and is only unsafe if unsafely used.
Indeed, there are hacks and they are some times necessary. The good thing about Haskell is, that hacks look like hacks.
In Modula-3 modules using hacks must be explicitly marked as UNSAFE. See http://www.cs.purdue.edu/homes/hosking/m3/reference/unsafe.html Maybe this is also an option for Haskell?
I don't think this is a good idea. It comes down to a question of whether you think it should be allowed for Haskell code to be used to write core Haskell libraries in a first-class manner. Perhaps you think libraries should always be in C in order to avoid the use of unsafePerformIO, but I prefer to allow them to be written in Haskell. But then, I don't see unsafePerformIO as inherently a hack. It's the only possible way that certain useful abstractions can be impelemented--at least, that's understanding. I'd be curious as to how much of the Prelude would be marked unsafe if you had your wish... David