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<pre><a name="line-1"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-2"></a><span class='hs-comment'>-- |</span>
<a name="line-3"></a><span class='hs-comment'>-- Copyright : (C) 2014-2016 Edward Kmett</span>
<a name="line-4"></a><span class='hs-comment'>-- License : BSD-style (see the file LICENSE)</span>
<a name="line-5"></a><span class='hs-comment'>-- Maintainer : Edward Kmett <ekmett@gmail.com></span>
<a name="line-6"></a><span class='hs-comment'>-- Stability : experimental</span>
<a name="line-7"></a><span class='hs-comment'>-- Portability : non-portable</span>
<a name="line-8"></a><span class='hs-comment'>--</span>
<a name="line-9"></a><span class='hs-comment'>-- One of most commonly-asked questions about this package is whether</span>
<a name="line-10"></a><span class='hs-comment'>-- it provides lenses for working with 'Data.Map.Map'. It does, but their uses</span>
<a name="line-11"></a><span class='hs-comment'>-- are perhaps obscured by their genericity. This module exists to provide</span>
<a name="line-12"></a><span class='hs-comment'>-- documentation for them.</span>
<a name="line-13"></a><span class='hs-comment'>--</span>
<a name="line-14"></a><span class='hs-comment'>-- 'Data.Map.Map' is an instance of 'Control.Lens.At.At', so we have a lenses</span>
<a name="line-15"></a><span class='hs-comment'>-- on values at keys:</span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-- >>> Map.fromList [(1, "world")] ^.at 1</span>
<a name="line-18"></a><span class='hs-comment'>-- Just "world"</span>
<a name="line-19"></a><span class='hs-comment'>--</span>
<a name="line-20"></a><span class='hs-comment'>-- >>> at 1 .~ Just "world" $ Map.empty</span>
<a name="line-21"></a><span class='hs-comment'>-- fromList [(1,"world")]</span>
<a name="line-22"></a><span class='hs-comment'>--</span>
<a name="line-23"></a><span class='hs-comment'>-- >>> at 0 ?~ "hello" $ Map.empty</span>
<a name="line-24"></a><span class='hs-comment'>-- fromList [(0,"hello")]</span>
<a name="line-25"></a><span class='hs-comment'>--</span>
<a name="line-26"></a><span class='hs-comment'>-- We can traverse, fold over, and map over key-value pairs in a</span>
<a name="line-27"></a><span class='hs-comment'>-- 'Data.Map.Map', thanks to its 'Control.Lens.Indexed.TraversableWithIndex',</span>
<a name="line-28"></a><span class='hs-comment'>-- 'Control.Lens.Indexed.FoldableWithIndex', and</span>
<a name="line-29"></a><span class='hs-comment'>-- 'Control.Lens.Indexed.FunctorWithIndex' instances.</span>
<a name="line-30"></a><span class='hs-comment'>--</span>
<a name="line-31"></a><span class='hs-comment'>-- >>> imap const $ Map.fromList [(1, "Venus")]</span>
<a name="line-32"></a><span class='hs-comment'>-- fromList [(1,1)]</span>
<a name="line-33"></a><span class='hs-comment'>--</span>
<a name="line-34"></a><span class='hs-comment'>-- >>> ifoldMap (\i _ -> Sum i) $ Map.fromList [(2, "Earth"), (3, "Mars")]</span>
<a name="line-35"></a><span class='hs-comment'>-- Sum {getSum = 5}</span>
<a name="line-36"></a><span class='hs-comment'>--</span>
<a name="line-37"></a><span class='hs-comment'>-- >>> itraverse_ (curry print) $ Map.fromList [(4, "Jupiter")]</span>
<a name="line-38"></a><span class='hs-comment'>-- (4,"Jupiter")</span>
<a name="line-39"></a><span class='hs-comment'>--</span>
<a name="line-40"></a><span class='hs-comment'>-- >>> itoList $ Map.fromList [(5, "Saturn")]</span>
<a name="line-41"></a><span class='hs-comment'>-- [(5,"Saturn")]</span>
<a name="line-42"></a><span class='hs-comment'>--</span>
<a name="line-43"></a><span class='hs-comment'>-- A related class, 'Control.Lens.At.Ixed', allows us to use</span>
<a name="line-44"></a><span class='hs-comment'>-- 'Control.Lens.At.ix' to traverse a value at a particular key.</span>
<a name="line-45"></a><span class='hs-comment'>--</span>
<a name="line-46"></a><span class='hs-comment'>-- >>> ix 2 %~ ("New " ++) $ Map.fromList [(2, "Earth")]</span>
<a name="line-47"></a><span class='hs-comment'>-- fromList [(2,"New Earth")]</span>
<a name="line-48"></a><span class='hs-comment'>--</span>
<a name="line-49"></a><span class='hs-comment'>-- >>> preview (ix 8) $ Map.empty</span>
<a name="line-50"></a><span class='hs-comment'>-- Nothing</span>
<a name="line-51"></a><span class='hs-comment'>--</span>
<a name="line-52"></a><span class='hs-comment'>-- Additionally, 'Data.Map.Map' has 'Control.Lens.Traversal.TraverseMin' and</span>
<a name="line-53"></a><span class='hs-comment'>-- 'Control.Lens.Traversal.TraverseMax' instances, which let us traverse over</span>
<a name="line-54"></a><span class='hs-comment'>-- the value at the least and greatest keys, respectively.</span>
<a name="line-55"></a><span class='hs-comment'>--</span>
<a name="line-56"></a><span class='hs-comment'>-- >>> preview traverseMin $ Map.fromList [(5, "Saturn"), (6, "Uranus")]</span>
<a name="line-57"></a><span class='hs-comment'>-- Just "Saturn"</span>
<a name="line-58"></a><span class='hs-comment'>--</span>
<a name="line-59"></a><span class='hs-comment'>-- >>> preview traverseMax $ Map.fromList [(5, "Saturn"), (6, "Uranus")]</span>
<a name="line-60"></a><span class='hs-comment'>-- Just "Uranus"</span>
<a name="line-61"></a><span class='hs-comment'>--</span>
<a name="line-62"></a><span class='hs-comment'>-----------------------------------------------------------------------------</span>
<a name="line-63"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Map</span><span class='hs-varop'>.</span><span class='hs-conid'>Lens</span>
<a name="line-64"></a> <span class='hs-layout'>(</span> <span class='hs-varid'>toMapOf</span>
<a name="line-65"></a> <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-66"></a>
<a name="line-67"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Lens</span><span class='hs-varop'>.</span><span class='hs-conid'>Getter</span> <span class='hs-layout'>(</span> <span class='hs-conid'>IndexedGetting</span><span class='hs-layout'>,</span> <span class='hs-varid'>iviews</span> <span class='hs-layout'>)</span>
<a name="line-68"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Map</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Map</span>
<a name="line-69"></a>
<a name="line-70"></a><span class='hs-comment'>-- $setup</span>
<a name="line-71"></a><span class='hs-comment'>-- >>> import Control.Lens</span>
<a name="line-72"></a><span class='hs-comment'>-- >>> import Data.Monoid</span>
<a name="line-73"></a><span class='hs-comment'>-- >>> :set -XNoOverloadedStrings</span>
<a name="line-74"></a>
<a name="line-75"></a><a name="toMapOf"></a><span class='hs-comment'>-- | Construct a map from a 'IndexedGetter', 'Control.Lens.Fold.IndexedFold', 'Control.Lens.Traversal.IndexedTraversal' or 'Control.Lens.Lens.IndexedLens'</span>
<a name="line-76"></a><span class='hs-comment'>--</span>
<a name="line-77"></a><span class='hs-comment'>-- The construction is left-biased (see 'Data.Map.Lazy.union'), i.e. the first</span>
<a name="line-78"></a><span class='hs-comment'>-- occurences of keys in the fold or traversal order are preferred.</span>
<a name="line-79"></a><span class='hs-comment'>--</span>
<a name="line-80"></a><span class='hs-comment'>-- >>> toMapOf folded ["hello", "world"]</span>
<a name="line-81"></a><span class='hs-comment'>-- fromList [(0,"hello"),(1,"world")]</span>
<a name="line-82"></a><span class='hs-comment'>--</span>
<a name="line-83"></a><span class='hs-comment'>-- >>> toMapOf (folded . ifolded) [('a',"alpha"),('b', "beta")]</span>
<a name="line-84"></a><span class='hs-comment'>-- fromList [('a',"alpha"),('b',"beta")]</span>
<a name="line-85"></a><span class='hs-comment'>--</span>
<a name="line-86"></a><span class='hs-comment'>-- >>> toMapOf (folded <.> folded) ["foo", "bar"]</span>
<a name="line-87"></a><span class='hs-comment'>-- fromList [((0,0),'f'),((0,1),'o'),((0,2),'o'),((1,0),'b'),((1,1),'a'),((1,2),'r')]</span>
<a name="line-88"></a><span class='hs-comment'>--</span>
<a name="line-89"></a><span class='hs-comment'>-- >>> toMapOf ifolded $ Map.fromList [('a', "hello"), ('b', "world")]</span>
<a name="line-90"></a><span class='hs-comment'>-- fromList [('a',"hello"),('b',"world")]</span>
<a name="line-91"></a><span class='hs-comment'>--</span>
<a name="line-92"></a><span class='hs-comment'>-- @</span>
<a name="line-93"></a><span class='hs-comment'>-- 'toMapOf' :: 'IndexedGetter' i s a -> s -> 'Map.Map' i a</span>
<a name="line-94"></a><span class='hs-comment'>-- 'toMapOf' :: 'Ord' i => 'IndexedFold' i s a -> s -> 'Map.Map' i a</span>
<a name="line-95"></a><span class='hs-comment'>-- 'toMapOf' :: 'IndexedLens'' i s a -> s -> 'Map.Map' i a</span>
<a name="line-96"></a><span class='hs-comment'>-- 'toMapOf' :: 'Ord' i => 'IndexedTraversal'' i s a -> s -> 'Map.Map' i a</span>
<a name="line-97"></a><span class='hs-comment'>-- @</span>
<a name="line-98"></a><span class='hs-definition'>toMapOf</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IndexedGetting</span> <span class='hs-varid'>i</span> <span class='hs-layout'>(</span><span class='hs-conid'>Map</span><span class='hs-varop'>.</span><span class='hs-conid'>Map</span> <span class='hs-varid'>i</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Map</span><span class='hs-varop'>.</span><span class='hs-conid'>Map</span> <span class='hs-varid'>i</span> <span class='hs-varid'>a</span>
<a name="line-99"></a><span class='hs-definition'>toMapOf</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>iviews</span> <span class='hs-varid'>l</span> <span class='hs-conid'>Map</span><span class='hs-varop'>.</span><span class='hs-varid'>singleton</span>
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