collecting requirements for FDs

[Henrik Nilsson]

Dear all,

Ross Peterson wrote:

 > The favourite customer for FDs has been the monad transformer library.
 > ...
 > What other libraries should Haskell' support, and what are their
 > requirements?

Here are some classes from Yampa/earlier versions of FRP.

I shouldn't think they're particularly demanding.

Also, I'm not saying these classes could not be defined
differently/better. They are just examples of what
seems to me reasonable uses of FDs.

---------------------------------------------------------

-- Minimal instance: zeroVector, (*^), (^+^), dot
class Floating a => VectorSpace v a | v -> a where
     zeroVector   :: v
     (*^)         :: a -> v -> v
     (^/)         :: v -> a -> v
     negateVector :: v -> v
     (^+^)        :: v -> v -> v
     (^-^)        :: v -> v -> v
     dot          :: v -> v -> a
     norm         :: v -> a
     normalize    :: v -> v

----------------------------------------------------------

-- Minimal instance: origin, .+^, .^.
class (Floating a, VectorSpace v a) =>
       AffineSpace p v a | p -> v, v -> a where
     origin   :: p
     (.+^)    :: p -> v -> p
     (.-^)    :: p -> v -> p
     (.-.)    :: p -> p -> v
     distance :: p -> p -> a

----------------------------------------------------------

 From an old version of FRP:

FRPCore.lhs:> class MixSwitchable s a b | s a -> b where
FRPCore.lhs:> class Switchable s i | s -> i where
FRPCore.lhs:  class RunningIn a b i | a -> i where
FRPCore.lhs:> class ImpAs a b | a -> b where
FRPTask.lhs:  class RunningInTask a t i | a t -> i where
FRPTask.lhs:> class Monad m => StateMonad s m | m -> s where
FRPTask.lhs:> class Monad m => EnvMonad env m | m -> env where
FRPTask.lhs:> class GTask t => MsgTask t m | t -> m where
FRPTask.lhs:> class MsgTaskMap mt m nt n | mt -> m, nt -> n where

/Henrik

-- 
Henrik Nilsson
School of Computer Science and Information Technology
The University of Nottingham
nhn at cs.nott.ac.uk

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