Bikeshedding: Would it be better to put the definition for +> (or better yet
<>) in the dictionary for Monoid with a circular definition for mappend?
That way new code defining Monoid instances can avoid ever having to even
mention mappend. I'm ok with it either way. I admit adding it to the
dictionary might add dictionary passing overhead and risk inconsistent
definitions of <> and mappend.
-Edward Kmett
On Tue, Jun 30, 2009 at 5:37 PM, Bryan O'Sullivan
Ticket: http://hackage.haskell.org/trac/ghc/ticket/3339
From the ticket:
This proposal was, I think, originally suggested by Jules Bean. The idea is to add two functions to the Data.Monoid module, (+>) and (<+), corresponding to different uses of mappend. These should not be methods of the Monoid typeclass, but top-level functions.
I hope (but slightly doubt) that the visual nature of the two operators might help to counter the thought that monoids are just for gluing things together.
(+>) :: (Monoid a) => a -> a -> a a +> b = a `mappend` b
(<+) :: (Monoid a) => a -> a -> a a <+ b = b `mappend` a
infixl 4 +> infixl 4 <+
Proposed deadline: two weeks.
If this looks reasonable, I'll attach darcs patches.
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