Re: [Haskell-cafe] ANN: data-category, restricted categories

On Fri, Mar 26, 2010 at 11:07 AM, Edward Kmett wrote:

On Fri, Mar 26, 2010 at 11:04 AM, Edward Kmett wrote:

...

-- as long as you're ignoring 'seq' terminateSeq :: a -> Unit terminateSeq a = a `seq` unit

Er ignore that language about seq. a `seq` unit is either another bottom or undefined, so there remains one canonical morphism even in the presence of seq (ignoring unsafePerformIO) =)

It all depends on how you define equality for functions. If you mean indistinguishable in contexts which may involve seq, then there are at least two values of type Unit -> (). foo :: (Unit -> ()) -> () foo x = x `seq` () foo terminate = () foo undefined = undefined Even this uses the convention that undefined = error "whatever" = loop, which isn't technically true, since you can use exception handling to write code which treats them differently. -- Dave Menendez http://www.eyrie.org/~zednenem/