David Roundy wrote:

hello, well that's because haskell is not as pure as it claims to be :-)

Nonsense. Haskell is perfectly pure; the IO monad is just nondeterministic :)

if every monad supports errors depends on what you mean by "supporting errors".

I mean `supporting errors' in the only possible sense that `supporting errors' can be implied by the existence of `fail': we have a throw function.

i would argue that supporting errors and divergence is not the same thing.

I never said it was.

the difference is that one should be able to handle an error thrown by a computation,

Although this doesn't imply the existence of a `catch' HOF; see the MonadPlus instance for Maybe.

while clearly we cannot detect nonterminating computations.

Of course. But we can detect exceptions thrown by `error'. Even though we can't distinguish them from non-termination /in pure Haskell/. We can of course distinguish them in the IO monad (which perhaps ought to be re-named the SinBin monad, to be more honest...). So we can detect erroneous computations in any monad. Jon Cast