The theory of mconcat is that it should handle monoids that need to be summed in some special way. I don't know if anyone actually uses it so, however. Still, Reid is right that the circular dependency sets a very high bar.
On Mon, Aug 31, 2015 at 1:54 PM, Fermin Reig <ferminreig@fastmail.fm> wrote:We could generalise:
mconcat:: [a] -> a
mconcat = foldr mappend memtpy
to:
mconcat:: Foldable t => t a -> a
mconcat = foldr mappend memtpy
-- even
-- mconcat = foldI don't understand the appeal of generalizing the type of a function when the generalization already exists; but in this case it's not a viable option anyways because mconcat is a class method of Monoid, and the definition of the Foldable class already refers to Monoid. Creating a circular dependency of Monoid on Foldable would be a headache best avoided.Regards,Reid Barton
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