Note that I already did this once as part of:
http://hackage.haskell.org/trac/ghc/ticket/4834
However, that never got merged.
So +1.
Bas
On 16 May 2013 13:33, David Luposchainsky
Hello everyone,
I recently went through GHC's source, and discovered there are quite a few instances of Monad that don't have Functor or Applicative instances. Fixing this is very easy by adding the standard instances (pure = return etc.), and will not break code.
There is one exception to this: Hoopl defines its own (<*>). However, since it does not seem to have any packages depend on it otherwise, renaming this operator is also easily done (the thing is only used ten times or so). I called it (<*|*>) to complement (|*><*|), but naming should be the least important issue here.
Small piece of backstory: The idea behind this is making GHC future-proof for changing Applicative to be a superclass of Monad. However, I think adding the Applicative instances is a good idea regardless of whether this will ever happen, so that's the only thing I'm proposing right now.
Greetings, David
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