    {-# LANGUAGE Rank2Types #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.IntSet.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.IntSet.Lens
      ( members
      , setmapped
      , setOf
      ) where

    import Control.Lens
    import Data.IntSet as IntSet

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

    -- | IntSet isn't Foldable, but this 'Fold' can be used to access the members of an 'IntSet'.
    --
    -- >>> sumOf members $ setOf folded [1,2,3,4]
    -- 10
    members :: Fold IntSet Int
    members = folding IntSet.toAscList
    {-# INLINE members #-}

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

    -- | Construct an 'IntSet' from a 'Getter', 'Fold', 'Traversal', 'Lens' or 'Iso'.
    --
    -- >>> setOf folded [1,2,3,4]
    -- fromList [1,2,3,4]
    --
    -- >>> setOf (folded._2) [("hello",1),("world",2),("!!!",3)]
    -- fromList [1,2,3]
    --
    -- @
    -- 'setOf' :: 'Getter' s 'Int'     -> s -> 'IntSet'
    -- 'setOf' :: 'Fold' s 'Int'       -> s -> 'IntSet'
    -- 'setOf' :: 'Iso'' s 'Int'       -> s -> 'IntSet'
    -- 'setOf' :: 'Lens'' s 'Int'      -> s -> 'IntSet'
    -- 'setOf' :: 'Traversal'' s 'Int' -> s -> 'IntSet'
    -- @
    setOf :: Getting IntSet s Int -> s -> IntSet
    setOf l = views l IntSet.singleton
    {-# INLINE setOf #-}