Flipping (give :: a -> (Given a => r) -> r) has type (r -> a -> r)
give from the reflection library has the following type
give :: forall a r. a -> (Given a => r) -> r
but flip give :: r -> a -> r
!
Same happens with our own Given
, give
$ ghci -ignore-dot-ghci -XRankNTypes
GHCi, version 8.3.20170605: http://www.haskell.org/ghc/ :? for help
Prelude> class Given a
Prelude> give :: a -> (Given a => r) -> r; give = undefined
Prelude> :t flip give
flip give :: c -> a -> c
Prelude>