    {-# LANGUAGE Rank2Types #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.Set.Lens
    -- Copyright   :  (C) 2012-13 Edward Kmett
    -- License     :  BSD-style (see the file LICENSE)
    -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
    -- Stability   :  provisional
    -- Portability :  portable
    --
    ----------------------------------------------------------------------------
    module Data.Set.Lens
      ( setmapped
      , setOf
      ) where

    import Control.Lens.Getter ( Getting, views )
    import Control.Lens.Setter ( setting )
    import Control.Lens.Type
    import Data.Set as Set

    -- $setup
    -- >>> :set -XNoOverloadedStrings
    -- >>> import Control.Lens

    -- | This 'Setter' can be used to change the type of a 'Set' by mapping
    -- the elements to new values.
    --
    -- Sadly, you can't create a valid 'Traversal' for a 'Set', but you can
    -- manipulate it by reading using 'Control.Lens.Fold.folded' and reindexing it via 'setmapped'.
    --
    -- >>> over setmapped (+1) (fromList [1,2,3,4])
    -- fromList [2,3,4,5]
    setmapped :: (Ord i, Ord j) => IndexPreservingSetter (Set i) (Set j) i j
    setmapped = setting Set.map
    {-# INLINE setmapped #-}

    -- | Construct a set from a 'Getter', 'Control.Lens.Fold.Fold', 'Control.Lens.Traversal.Traversal', 'Control.Lens.Lens.Lens' or 'Control.Lens.Iso.Iso'.
    --
    -- >>> setOf folded ["hello","world"]
    -- fromList ["hello","world"]
    --
    -- >>> setOf (folded._2) [("hello",1),("world",2),("!!!",3)]
    -- fromList [1,2,3]
    --
    -- @
    -- 'setOf' ::          'Getter' s a     -> s -> 'Set' a
    -- 'setOf' :: 'Ord' a => 'Fold' s a       -> s -> 'Set' a
    -- 'setOf' ::          'Iso'' s a       -> s -> 'Set' a
    -- 'setOf' ::          'Lens'' s a      -> s -> 'Set' a
    -- 'setOf' :: 'Ord' a => 'Traversal'' s a -> s -> 'Set' a
    -- @
    setOf :: Getting (Set a) s a -> s -> Set a
    setOf l = views l Set.singleton
    {-# INLINE setOf #-}