On Sun, Sep 5, 2010 at 7:47 AM, Ivan Lazar Miljenovic < ivan.miljeno...@gmail.com> wrote:
> On 5 September 2010 22:40, John Lato <jwl...@gmail.com> wrote: > > > > Having Pointed is categorically the right thing to do, which is why I > argue > > for its inclusion. Also, I think it would be prudent to avoid a > situation > > with the possibility of turning into a rehash of the > > Functor/Applicative/Monad mess. > > > > Are there any good reasons for not including it? Just because we don't > have > > a use now doesn't mean it might not be useful in the future. > > Only reason I can think of: it's a pain to make useless class > instances when there is no reason why they can't be combined (since > you never make an instance of one without an instance of the other). > It's a one-time cost, though, so to me at least it's not a big deal. > I _can_ think of a data type that could conceivably be an instance of > Pointed but not Applicative: a BloomFilter (though there's not really > any point in having a BloomFilter with only one value that I can see, > but maybe someone can since there's the singletonB function). > Thanks for mentioning this. Bloom filters certainly are an interesting structure, in many ways. John
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