But if one did start considering bottom to be a value, one would have to distinguish different ones. For instance, (error "ABC") vs. (error "PQR"). Obviously this is not finite.
Nor is it computable, since it must distinguish terminating programs
from nonterminating ones (i.e. the halting problem).
On a side note, since "instance (Finite a, Finite b) => Finite (a ->
b)" should be possible, one can even compare some higher order
functions with this approach ;).
On 14 April 2010 09:29, Ashley Yakeley
On Wed, 2010-04-14 at 08:13 +0100, Thomas Davie wrote:
Your instances of Finite are not quite right:
bottom :: a bottom = doSomethingToLoopInfinitely.
instance Finite () where allValues = [(), bottom]
Bottom is not a value, it's failure to evaluate to a value.
But if one did start considering bottom to be a value, one would have to distinguish different ones. For instance, (error "ABC") vs. (error "PQR"). Obviously this is not finite.
-- Ashley Yakeley
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe