    -----------------------------------------------------------------------------
    -- |
    -- Copyright   :  (C) 2014-2016 Edward Kmett
    -- License     :  BSD-style (see the file LICENSE)
    -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
    -- Stability   :  experimental
    -- Portability :  non-portable
    --
    -- One of most commonly-asked questions about this package is whether
    -- it provides lenses for working with 'Data.Map.Map'. It does, but their uses
    -- are perhaps obscured by their genericity. This module exists to provide
    -- documentation for them.
    --
    -- 'Data.Map.Map' is an instance of 'Control.Lens.At.At', so we have a lenses
    -- on values at keys:
    --
    -- >>> Map.fromList [(1, "world")] ^.at 1
    -- Just "world"
    --
    -- >>> at 1 .~ Just "world" $ Map.empty
    -- fromList [(1,"world")]
    --
    -- >>> at 0 ?~ "hello" $ Map.empty
    -- fromList [(0,"hello")]
    --
    -- We can traverse, fold over, and map over key-value pairs in a
    -- 'Data.Map.Map', thanks to its 'Control.Lens.Indexed.TraversableWithIndex',
    -- 'Control.Lens.Indexed.FoldableWithIndex', and
    -- 'Control.Lens.Indexed.FunctorWithIndex' instances.
    --
    -- >>> imap const $ Map.fromList [(1, "Venus")]
    -- fromList [(1,1)]
    --
    -- >>> ifoldMap (\i _ -> Sum i) $ Map.fromList [(2, "Earth"), (3, "Mars")]
    -- Sum {getSum = 5}
    --
    -- >>> itraverse_ (curry print) $ Map.fromList [(4, "Jupiter")]
    -- (4,"Jupiter")
    --
    -- >>> itoList $ Map.fromList [(5, "Saturn")]
    -- [(5,"Saturn")]
    --
    -- A related class, 'Control.Lens.At.Ixed', allows us to use
    -- 'Control.Lens.At.ix' to traverse a value at a particular key.
    --
    -- >>> ix 2 %~ ("New " ++) $ Map.fromList [(2, "Earth")]
    -- fromList [(2,"New Earth")]
    --
    -- >>> preview (ix 8) $ Map.empty
    -- Nothing
    --
    -- Additionally, 'Data.Map.Map' has 'Control.Lens.Traversal.TraverseMin' and
    -- 'Control.Lens.Traversal.TraverseMax' instances, which let us traverse over
    -- the value at the least and greatest keys, respectively.
    --
    -- >>> preview traverseMin $ Map.fromList [(5, "Saturn"), (6, "Uranus")]
    -- Just "Saturn"
    --
    -- >>> preview traverseMax $ Map.fromList [(5, "Saturn"), (6, "Uranus")]
    -- Just "Uranus"
    --
    -----------------------------------------------------------------------------
    module Data.Map.Lens
      ( toMapOf
      ) where

    import Control.Lens.Getter ( IndexedGetting, iviews )
    import qualified Data.Map as Map

    -- $setup
    -- >>> import Control.Lens
    -- >>> import Data.Monoid
    -- >>> import qualified Data.Map as Map
    -- >>> :set -XNoOverloadedStrings

    -- | Construct a map from a 'IndexedGetter', 'Control.Lens.Fold.IndexedFold', 'Control.Lens.Traversal.IndexedTraversal' or 'Control.Lens.Lens.IndexedLens'
    --
    -- The construction is left-biased (see 'Data.Map.Lazy.union'), i.e. the first
    -- occurrences of keys in the fold or traversal order are preferred.
    --
    -- >>> toMapOf folded ["hello", "world"]
    -- fromList [(0,"hello"),(1,"world")]
    --
    -- >>> toMapOf (folded . ifolded) [('a',"alpha"),('b', "beta")]
    -- fromList [('a',"alpha"),('b',"beta")]
    --
    -- >>> toMapOf (folded <.> folded) ["foo", "bar"]
    -- fromList [((0,0),'f'),((0,1),'o'),((0,2),'o'),((1,0),'b'),((1,1),'a'),((1,2),'r')]
    --
    -- >>> toMapOf ifolded $ Map.fromList [('a', "hello"), ('b', "world")]
    -- fromList [('a',"hello"),('b',"world")]
    --
    -- @
    -- 'toMapOf' ::          'IndexedGetter' i s a     -> s -> 'Map.Map' i a
    -- 'toMapOf' :: 'Ord' i => 'IndexedFold' i s a       -> s -> 'Map.Map' i a
    -- 'toMapOf' ::          'IndexedLens'' i s a      -> s -> 'Map.Map' i a
    -- 'toMapOf' :: 'Ord' i => 'IndexedTraversal'' i s a -> s -> 'Map.Map' i a
    -- @
    toMapOf :: IndexedGetting i (Map.Map i a) s a -> s -> Map.Map i a
    toMapOf :: forall i a s. IndexedGetting i (Map i a) s a -> s -> Map i a
    toMapOf IndexedGetting i (Map i a) s a
    l = IndexedGetting i (Map i a) s a
    -> (i -> a -> Map i a) -> s -> Map i a
    forall s (m :: * -> *) i r a.
    MonadReader s m =>
    IndexedGetting i r s a -> (i -> a -> r) -> m r
    iviews IndexedGetting i (Map i a) s a
    l i -> a -> Map i a
    forall k a. k -> a -> Map k a
    Map.singleton