* Gabriel Gonzalez
On 12/27/2012 02:25 PM, Roman Cheplyaka wrote:
Wouldn't it be better to have a real algebraic type instead of wrapping Maybe?
Something like
data Maximum a = MinusInfinity | Maximum a data Minimum a = PlusInfinity | Minimum a
Maximum x is more concise than Maximum (Just x), and MinusInfinity is more descriptive than Maximum Nothing. getMaximum/getMinimum functions can still return Maybes.
Anyway, I'm +1 to having something along these lines.
Roman
Interesting. Then you can recapitulate the original Maybe API using:
getMaximum :: Maximum a -> Maybe a getMinimum :: Minimum a -> Maybe a
One slight disadvantage is that there might be a tiny overhead for converting between Maximum/Minimum and Maybe, but I doubt that would be a bottle-neck in any application.
But the type isn't abstract, so nothing prevents one from using direct pattern matching in tight loops.
Another disadvantage is then it sets a precedent for redefining the First and Last Monoids to similarly more descriptive types. When I did it the Maybe way I was just copying the way First and Last worked.
I don't think the analogy holds. First and Last are wrappers for Maybe by intention — they are needed because we can't have two different instances for Maybe (although both of them make sense). In this case, however, Maybe is used artificially to "lift" numbers. Monoidal instance for Maybe corresponding to 'max' would look rather weird. Finally, we have nice names for mempty of Maximum/Minimum but not of First/Last. Roman