Aaron McDaid wrote:
Could seq be changed so that it will not give an error if it finds undefined?
The definition of seq is that seq _|_ x = _|_. That is what it is supposed to do. Actually, the behavior of seq on undefined is very tame - it raises an exception which can be caught. Sometimes seq hangs. Unfortunately, getting around that would require solving the halting problem.
Am I right in thinking that seq is supposed to theoretically do nothing, but simply give a hint to the compiler so to speak?
I see it the other way around. Theoretically, seq does a lot. In practice, it is up to each compiler to decide on the implementation details.
Anyway, as far as I can see it is already true that (>>= f) . return = f because 'equality' for Monads simply means they do that same thing when 'executed' or whatever. The only thing that can currently find a difference between the above monads is seq and seq is a funny thing.
That does seem to be a pretty widespread view. I am a relative newcomer to Haskell, so I guess I am naive. But, so far, I am not convinced. Haskell is a non-strict language, so non-strict values are legitimate, and so is seq. I don't see how seq is any more funny than irrational numbers are irrational or imaginary numbers are imaginary. Regards, Yitz