Jake McArthur wrote:
The monoids package offers something similar to this:
mapReduce :: (Generator c, Reducer e m) => (Elem c -> e) -> c -> m
If we take (Elem c) to be (item), (e) to be (item'), (c) to be (full), and (m) to be (full'), it's basically the same thing, and offers the same advantages as the ones you listed, as far as I can tell.
Your example about uvector inspired me to try writing out the necessary instances for uvector: instance UA a => Monoid (UArr a) where mempty = emptyU mappend = appendU instance UA a => Reducer a (UArr a) where unit = singletonU snoc = snocU cons = consU instance UA a => Generator (UArr a) where type Elem (UArr a) = a mapTo f = foldlU (\a -> snoc a . f) - Jake