    {-# LANGUAGE CPP #-}
    {-# LANGUAGE Rank2Types #-}
    #ifdef TRUSTWORTHY
    {-# LANGUAGE Trustworthy #-}
    #endif
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.HashSet.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.HashSet.Lens
      ( setmapped
      , setOf
      ) where

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

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

    -- | This 'Setter' can be used to change the type of a 'HashSet' 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'.
    setmapped :: (Eq i, Hashable i, Eq j, Hashable j) => IndexPreservingSetter (HashSet i) (HashSet j) i j
    setmapped = setting HashSet.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' :: 'Hashable' a         => 'Getter' s a     -> s -> 'HashSet' a
    -- 'setOf' :: ('Eq' a, 'Hashable' a) => 'Fold' s a       -> s -> 'HashSet' a
    -- 'setOf' :: 'Hashable' a         => 'Iso'' s a       -> s -> 'HashSet' a
    -- 'setOf' :: 'Hashable' a         => 'Lens'' s a      -> s -> 'HashSet' a
    -- 'setOf' :: ('Eq' a, 'Hashable' a) => 'Traversal'' s a -> s -> 'HashSet' a
    -- @
    setOf :: Hashable a => Getting (HashSet a) s a -> s -> HashSet a
    setOf l = views l HashSet.singleton
    {-# INLINE setOf #-}