selective applicative functors

 Selective applicative functors: declare your effects statically,
 select which to execute dynamically.
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 This is a library for selective applicative functors, or just
 "selective functors" for short, an abstraction between
 applicative functors and monads.
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 This package provides a library for the Haskell programming language.
 See http://www.haskell.org/ for more information on Haskell.