Personally I like having both Maximum-and-Minimum-with-sentinel version
like the proposed Maximum and Minimum here, along with the simpler Max and
Min semigroups that upgrade themselves to a Monoid when Bounded is present.
Each is useful for different usecases. I like having access to the
efficient version whenever I know the target admits a minimum value (like
Int).
Paying for unnecessary Maybe's makes me cry.
-Edward
On Fri, Dec 28, 2012 at 4:39 PM, Gabriel Gonzalez
I'm still not convinced by the Bounded instance for Maybe, which seems like a hack. I would prefer to just use the Monoid instance for "Maybe (Max a)" and just fmap "getMaximum" over the result rather than pretend that Maybe is Bounded when it's not.
Moreover, the entire Bounded constraint seems wrong in principle. There is no intuitive reason why some type should be bounded to be able to take a maximum of a set of elements. The Ord constraint should be sufficient to define a maximum.
I also don't think it is a good idea to have direct Monoid instances for Max and Min, because they behave weirdly on empty lists. Do you really think that "minimum [] :: Int" should be defined? I still believe that the correct answer for "minimum []" should be Nothing or a similar type with a distinguished infinity like those that Roman proposed.``
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