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<title>Data/List/PointedList.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE TemplateHaskell, TypeOperators #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>-- | An implementation of a zipper-like non-empty list structure that tracks</span>
<a name="line-4"></a><span class='hs-comment'>-- an index position in the list (the 'focus').</span>
<a name="line-5"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span><span class='hs-varop'>.</span><span class='hs-conid'>PointedList</span> <span class='hs-keyword'>where</span>
<a name="line-6"></a>
<a name="line-7"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Prelude</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>foldl</span><span class='hs-layout'>,</span> <span class='hs-varid'>foldr</span><span class='hs-layout'>,</span> <span class='hs-varid'>elem</span><span class='hs-layout'>)</span>
<a name="line-8"></a>
<a name="line-9"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Applicative</span>
<a name="line-10"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span>
<a name="line-11"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Binary</span>
<a name="line-12"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>DeriveTH</span>
<a name="line-13"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Foldable</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>find</span><span class='hs-layout'>)</span>
<a name="line-14"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span> <span class='hs-varid'>hiding</span> <span class='hs-layout'>(</span><span class='hs-varid'>length</span><span class='hs-layout'>,</span> <span class='hs-varid'>foldl</span><span class='hs-layout'>,</span> <span class='hs-varid'>foldr</span><span class='hs-layout'>,</span> <span class='hs-varid'>find</span><span class='hs-layout'>,</span> <span class='hs-varid'>elem</span><span class='hs-layout'>)</span>
<a name="line-15"></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'>List</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>List</span>
<a name="line-16"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Maybe</span>
<a name="line-17"></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'>Label</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Label</span>
<a name="line-18"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Traversable</span>
<a name="line-19"></a>
<a name="line-20"></a><a name="PointedList"></a><span class='hs-comment'>-- | The implementation of the pointed list structure which tracks the current</span>
<a name="line-21"></a><a name="PointedList"></a><span class='hs-comment'>-- position in the list structure.</span>
<a name="line-22"></a><a name="PointedList"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span>
<a name="line-23"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>reversedPrefix</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span>
<a name="line-24"></a> <span class='hs-layout'>,</span> <span class='hs-sel'>_focus</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span>
<a name="line-25"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>suffix</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span>
<a name="line-26"></a> <span class='hs-layout'>}</span> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span><span class='hs-layout'>)</span>
<a name="line-27"></a>
<a name="line-28"></a><span class='hs-varop'>$</span><span class='hs-layout'>(</span><span class='hs-varid'>derive</span> <span class='hs-varid'>makeBinary</span> <span class='hs-chr'>'</span><span class='hs-chr'>'</span><span class='hs-conid'>PointedList</span><span class='hs-layout'>)</span>
<a name="line-29"></a><span class='hs-varop'>$</span><span class='hs-layout'>(</span><span class='hs-conid'>Label</span><span class='hs-varop'>.</span><span class='hs-varid'>mkLabels</span> <span class='hs-keyglyph'>[</span><span class='hs-chr'>'</span><span class='hs-chr'>'</span><span class='hs-conid'>PointedList</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span>
<a name="line-30"></a>
<a name="line-31"></a><a name="instance%20Show%20(PointedList%20a)"></a><span class='hs-keyword'>instance</span> <span class='hs-layout'>(</span><span class='hs-conid'>Show</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Show</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-32"></a> <span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-varid'>reverse</span> <span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span> <span class='hs-str'>" "</span> <span class='hs-varop'>++</span> <span class='hs-varid'>show</span> <span class='hs-varid'>x</span> <span class='hs-varop'>++</span> <span class='hs-str'>" "</span> <span class='hs-varop'>++</span> <span class='hs-varid'>show</span> <span class='hs-varid'>rs</span>
<a name="line-33"></a>
<a name="line-34"></a><a name="instance%20Functor%20PointedList"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Functor</span> <span class='hs-conid'>PointedList</span> <span class='hs-keyword'>where</span>
<a name="line-35"></a> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-varid'>f</span> <span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-varid'>f</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span>
<a name="line-36"></a>
<a name="line-37"></a><a name="instance%20Foldable%20PointedList"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Foldable</span> <span class='hs-conid'>PointedList</span> <span class='hs-keyword'>where</span>
<a name="line-38"></a> <span class='hs-varid'>foldr</span> <span class='hs-varid'>f</span> <span class='hs-varid'>z</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldl</span> <span class='hs-layout'>(</span><span class='hs-varid'>flip</span> <span class='hs-varid'>f</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>foldr</span> <span class='hs-varid'>f</span> <span class='hs-varid'>z</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>ls</span>
<a name="line-39"></a>
<a name="line-40"></a><a name="instance%20Traversable%20PointedList"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Traversable</span> <span class='hs-conid'>PointedList</span> <span class='hs-keyword'>where</span>
<a name="line-41"></a> <span class='hs-varid'>traverse</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-varop'><$></span>
<a name="line-42"></a> <span class='hs-layout'>(</span><span class='hs-varid'>reverse</span> <span class='hs-varop'><$></span> <span class='hs-varid'>traverse</span> <span class='hs-varid'>f</span> <span class='hs-layout'>(</span><span class='hs-varid'>reverse</span> <span class='hs-varid'>ls</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'><*></span> <span class='hs-varid'>f</span> <span class='hs-varid'>x</span> <span class='hs-varop'><*></span> <span class='hs-varid'>traverse</span> <span class='hs-varid'>f</span> <span class='hs-varid'>rs</span>
<a name="line-43"></a>
<a name="line-44"></a><a name="singleton"></a><span class='hs-comment'>-- | Create a 'PointedList' with a single element.</span>
<a name="line-45"></a><span class='hs-definition'>singleton</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-46"></a><span class='hs-definition'>singleton</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>x</span> <span class='hs-conid'>[]</span>
<a name="line-47"></a>
<a name="line-48"></a><a name="fromList"></a><span class='hs-comment'>-- | Possibly create a @'Just' 'PointedList'@ if the provided list has at least</span>
<a name="line-49"></a><span class='hs-comment'>-- one element; otherwise, return Nothing.</span>
<a name="line-50"></a><span class='hs-comment'>--</span>
<a name="line-51"></a><span class='hs-comment'>-- The provided list's head will be the focus of the list, and the rest of</span>
<a name="line-52"></a><span class='hs-comment'>-- list will follow on the right side.</span>
<a name="line-53"></a><span class='hs-definition'>fromList</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-54"></a><span class='hs-definition'>fromList</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-55"></a><span class='hs-definition'>fromList</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>x</span> <span class='hs-varid'>xs</span>
<a name="line-56"></a>
<a name="line-57"></a><a name="fromListEnd"></a><span class='hs-comment'>-- | Possibly create a @'Just' 'PointedList'@ if the provided list has at least</span>
<a name="line-58"></a><span class='hs-comment'>-- one element; otherwise, return Nothing.</span>
<a name="line-59"></a><span class='hs-comment'>--</span>
<a name="line-60"></a><span class='hs-comment'>-- The provided list's last element will be the focus of the list, following</span>
<a name="line-61"></a><span class='hs-comment'>-- the rest of the list in order, to the left.</span>
<a name="line-62"></a><span class='hs-definition'>fromListEnd</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-63"></a><span class='hs-definition'>fromListEnd</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-64"></a><span class='hs-definition'>fromListEnd</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>xs'</span> <span class='hs-varid'>x</span> <span class='hs-conid'>[]</span>
<a name="line-65"></a> <span class='hs-keyword'>where</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>xs'</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>reverse</span> <span class='hs-varid'>xs</span>
<a name="line-66"></a>
<a name="line-67"></a><a name="replace"></a><span class='hs-comment'>-- | Replace the focus of the list, retaining the prefix and suffix.</span>
<a name="line-68"></a><span class='hs-definition'>replace</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-69"></a><span class='hs-definition'>replace</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Label</span><span class='hs-varop'>.</span><span class='hs-varid'>set</span> <span class='hs-varid'>focus</span>
<a name="line-70"></a>
<a name="line-71"></a><a name="next"></a><span class='hs-comment'>-- | Possibly move the focus to the next element in the list.</span>
<a name="line-72"></a><span class='hs-definition'>next</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-73"></a><span class='hs-definition'>next</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-74"></a><span class='hs-definition'>next</span> <span class='hs-varid'>p</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varop'>.</span> <span class='hs-varid'>tryNext</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span> <span class='hs-comment'>-- GHC doesn't allow PL form here</span>
<a name="line-75"></a>
<a name="line-76"></a><a name="tryNext"></a><span class='hs-comment'>-- | Attempt to move the focus to the next element, or 'error' if there are</span>
<a name="line-77"></a><span class='hs-comment'>-- no more elements.</span>
<a name="line-78"></a><span class='hs-definition'>tryNext</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-79"></a><span class='hs-definition'>tryNext</span> <span class='hs-varid'>p</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>error</span> <span class='hs-str'>"cannot move to next element"</span>
<a name="line-80"></a><span class='hs-definition'>tryNext</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span> <span class='hs-varid'>rs</span>
<a name="line-81"></a>
<a name="line-82"></a><a name="previous"></a><span class='hs-comment'>-- | Possibly move the focus to the previous element in the list.</span>
<a name="line-83"></a><span class='hs-definition'>previous</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-84"></a><span class='hs-definition'>previous</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-85"></a><span class='hs-definition'>previous</span> <span class='hs-varid'>p</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varop'>.</span> <span class='hs-varid'>tryPrevious</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span>
<a name="line-86"></a>
<a name="line-87"></a><a name="tryPrevious"></a><span class='hs-comment'>-- | Attempt to move the focus to the previous element, or 'error' if there are</span>
<a name="line-88"></a><span class='hs-comment'>-- no more elements.</span>
<a name="line-89"></a><span class='hs-definition'>tryPrevious</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-90"></a><span class='hs-definition'>tryPrevious</span> <span class='hs-varid'>p</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-91"></a> <span class='hs-varid'>error</span> <span class='hs-str'>"cannot move to previous element"</span>
<a name="line-92"></a><span class='hs-definition'>tryPrevious</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>l</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>l</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span>
<a name="line-93"></a>
<a name="line-94"></a><a name="insert"></a><span class='hs-comment'>-- | An alias for 'insertRight'.</span>
<a name="line-95"></a><span class='hs-definition'>insert</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-96"></a><span class='hs-definition'>insert</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>insertRight</span>
<a name="line-97"></a>
<a name="line-98"></a><a name="insertLeft"></a><span class='hs-comment'>-- | Insert an element to the left of the focus, then move the focus to the new</span>
<a name="line-99"></a><span class='hs-comment'>-- element.</span>
<a name="line-100"></a><span class='hs-definition'>insertLeft</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-101"></a><span class='hs-definition'>insertLeft</span> <span class='hs-varid'>y</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>y</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span>
<a name="line-102"></a>
<a name="line-103"></a><a name="insertRight"></a><span class='hs-comment'>-- | Insert an element to the right of the focus, then move the focus to the</span>
<a name="line-104"></a><span class='hs-comment'>-- new element.</span>
<a name="line-105"></a><span class='hs-definition'>insertRight</span> <span class='hs-keyglyph'>::</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-106"></a><span class='hs-definition'>insertRight</span> <span class='hs-varid'>y</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-varid'>y</span> <span class='hs-varid'>rs</span>
<a name="line-107"></a>
<a name="line-108"></a><a name="delete"></a><span class='hs-comment'>-- | An alias of 'deleteRight'.</span>
<a name="line-109"></a><span class='hs-definition'>delete</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-110"></a><span class='hs-definition'>delete</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>deleteRight</span>
<a name="line-111"></a>
<a name="line-112"></a><a name="deleteLeft"></a><span class='hs-comment'>-- | Possibly delete the element at the focus, then move the element on the</span>
<a name="line-113"></a><span class='hs-comment'>-- left to the focus. If no element is on the left, focus on the element to</span>
<a name="line-114"></a><span class='hs-comment'>-- the right. If the deletion will cause the list to be empty, return</span>
<a name="line-115"></a><span class='hs-comment'>-- 'Nothing'.</span>
<a name="line-116"></a><span class='hs-definition'>deleteLeft</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-117"></a><span class='hs-definition'>deleteLeft</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-118"></a><span class='hs-definition'>deleteLeft</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>l</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>l</span> <span class='hs-varid'>rs</span>
<a name="line-119"></a><span class='hs-definition'>deleteLeft</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>r</span> <span class='hs-varid'>rs</span>
<a name="line-120"></a>
<a name="line-121"></a><a name="deleteRight"></a><span class='hs-comment'>-- | Possibly delete the element at the focus, then move the element on the</span>
<a name="line-122"></a><span class='hs-comment'>-- right to the focus. If no element is on the right, focus on the element to</span>
<a name="line-123"></a><span class='hs-comment'>-- the left. If the deletion will cause the list to be empty, return</span>
<a name="line-124"></a><span class='hs-comment'>-- 'Nothing'.</span>
<a name="line-125"></a><span class='hs-definition'>deleteRight</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-126"></a><span class='hs-definition'>deleteRight</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-127"></a><span class='hs-definition'>deleteRight</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>r</span> <span class='hs-varid'>rs</span>
<a name="line-128"></a><span class='hs-definition'>deleteRight</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>l</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>l</span> <span class='hs-conid'>[]</span>
<a name="line-129"></a>
<a name="line-130"></a><a name="deleteOthers"></a><span class='hs-comment'>-- | Delete all elements in the list except the focus.</span>
<a name="line-131"></a><span class='hs-definition'>deleteOthers</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span>
<a name="line-132"></a><span class='hs-definition'>deleteOthers</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>b</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>b</span> <span class='hs-conid'>[]</span>
<a name="line-133"></a>
<a name="line-134"></a><a name="length"></a><span class='hs-comment'>-- | The length of the list.</span>
<a name="line-135"></a><span class='hs-definition'>length</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Int</span>
<a name="line-136"></a><span class='hs-definition'>length</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldr</span> <span class='hs-layout'>(</span><span class='hs-varid'>const</span> <span class='hs-layout'>(</span><span class='hs-varop'>+</span><span class='hs-num'>1</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-num'>0</span>
<a name="line-137"></a>
<a name="line-138"></a><a name="atStart"></a><span class='hs-comment'>-- | Whether the focus is the first element.</span>
<a name="line-139"></a><span class='hs-definition'>atStart</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-140"></a><span class='hs-definition'>atStart</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-141"></a><span class='hs-definition'>atStart</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-142"></a>
<a name="line-143"></a><a name="atEnd"></a><span class='hs-comment'>-- | Whether the focus is the last element.</span>
<a name="line-144"></a><span class='hs-definition'>atEnd</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-145"></a><span class='hs-definition'>atEnd</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-146"></a><span class='hs-definition'>atEnd</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-147"></a>
<a name="line-148"></a><a name="positions"></a><span class='hs-comment'>-- | Create a 'PointedList' of variations of the provided 'PointedList', in</span>
<a name="line-149"></a><span class='hs-comment'>-- which each element is focused, with the provided 'PointedList' as the</span>
<a name="line-150"></a><span class='hs-comment'>-- focus of the sets.</span>
<a name="line-151"></a><span class='hs-definition'>positions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-152"></a><span class='hs-definition'>positions</span> <span class='hs-varid'>p</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>x</span> <span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>left</span> <span class='hs-varid'>p</span> <span class='hs-varid'>right</span>
<a name="line-153"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>left</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unfoldr</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>p</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>join</span> <span class='hs-conid'>(,)</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>previous</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span>
<a name="line-154"></a> <span class='hs-varid'>right</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unfoldr</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>p</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>join</span> <span class='hs-conid'>(,)</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>next</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span>
<a name="line-155"></a>
<a name="line-156"></a><a name="contextMap"></a><span class='hs-comment'>-- | Map over the 'PointedList's created via 'positions', such that @f@ is </span>
<a name="line-157"></a><span class='hs-comment'>-- called with each element of the list focused in the provided</span>
<a name="line-158"></a><span class='hs-comment'>-- 'PointedList'. An example makes this easier to understand:</span>
<a name="line-159"></a><span class='hs-comment'>--</span>
<a name="line-160"></a><span class='hs-comment'>-- > contextMap atStart (fromJust $ fromList [1..5])</span>
<a name="line-161"></a><span class='hs-definition'>contextMap</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>b</span>
<a name="line-162"></a><span class='hs-definition'>contextMap</span> <span class='hs-varid'>f</span> <span class='hs-varid'>z</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmap</span> <span class='hs-varid'>f</span> <span class='hs-varop'>$</span> <span class='hs-varid'>positions</span> <span class='hs-varid'>z</span>
<a name="line-163"></a>
<a name="line-164"></a><a name="withFocus"></a><span class='hs-comment'>-- | Create a @'PointedList' a@ of @(a, 'Bool')@, in which the boolean values</span>
<a name="line-165"></a><span class='hs-comment'>-- specify whether the current element has the focus. That is, all of the</span>
<a name="line-166"></a><span class='hs-comment'>-- booleans will be 'False', except the focused element.</span>
<a name="line-167"></a><span class='hs-definition'>withFocus</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-layout'>,</span> <span class='hs-conid'>Bool</span><span class='hs-layout'>)</span>
<a name="line-168"></a><span class='hs-definition'>withFocus</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-169"></a> <span class='hs-conid'>PointedList</span> <span class='hs-layout'>(</span><span class='hs-varid'>zip</span> <span class='hs-varid'>a</span> <span class='hs-layout'>(</span><span class='hs-varid'>repeat</span> <span class='hs-conid'>False</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span><span class='hs-layout'>,</span> <span class='hs-conid'>True</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>zip</span> <span class='hs-varid'>c</span> <span class='hs-layout'>(</span><span class='hs-varid'>repeat</span> <span class='hs-conid'>False</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-170"></a>
<a name="line-171"></a><a name="moveTo"></a><span class='hs-comment'>-- | Move the focus to the specified index. The first element is at index 0.</span>
<a name="line-172"></a><span class='hs-definition'>moveTo</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Int</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-173"></a><span class='hs-definition'>moveTo</span> <span class='hs-varid'>n</span> <span class='hs-varid'>pl</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>moveN</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span> <span class='hs-comment'>-</span> <span class='hs-layout'>(</span><span class='hs-varid'>index</span> <span class='hs-varid'>pl</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varid'>pl</span>
<a name="line-174"></a>
<a name="line-175"></a><a name="moveN"></a><span class='hs-comment'>-- | Move the focus by @n@, relative to the current index. Negative values move</span>
<a name="line-176"></a><span class='hs-comment'>-- the focus backwards, positive values more forwards through the list.</span>
<a name="line-177"></a><span class='hs-definition'>moveN</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Int</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-178"></a><span class='hs-definition'>moveN</span> <span class='hs-varid'>n</span> <span class='hs-varid'>pl</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>left</span> <span class='hs-varid'>x</span> <span class='hs-varid'>right</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>go</span> <span class='hs-varid'>n</span> <span class='hs-varid'>left</span> <span class='hs-varid'>x</span> <span class='hs-varid'>right</span>
<a name="line-179"></a> <span class='hs-keyword'>where</span>
<a name="line-180"></a> <span class='hs-varid'>go</span> <span class='hs-varid'>n</span> <span class='hs-varid'>left</span> <span class='hs-varid'>x</span> <span class='hs-varid'>right</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>compare</span> <span class='hs-varid'>n</span> <span class='hs-num'>0</span> <span class='hs-keyword'>of</span>
<a name="line-181"></a> <span class='hs-conid'>GT</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>right</span> <span class='hs-keyword'>of</span>
<a name="line-182"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-183"></a> <span class='hs-layout'>(</span><span class='hs-varid'>r</span><span class='hs-conop'>:</span><span class='hs-varid'>rs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>go</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span><span class='hs-comment'>-</span><span class='hs-num'>1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>left</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span> <span class='hs-varid'>rs</span>
<a name="line-184"></a> <span class='hs-conid'>LT</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyword'>case</span> <span class='hs-varid'>left</span> <span class='hs-keyword'>of</span>
<a name="line-185"></a> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Nothing</span>
<a name="line-186"></a> <span class='hs-layout'>(</span><span class='hs-varid'>l</span><span class='hs-conop'>:</span><span class='hs-varid'>ls</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>go</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span><span class='hs-varop'>+</span><span class='hs-num'>1</span><span class='hs-layout'>)</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>l</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>right</span><span class='hs-layout'>)</span>
<a name="line-187"></a> <span class='hs-conid'>EQ</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>left</span> <span class='hs-varid'>x</span> <span class='hs-varid'>right</span>
<a name="line-188"></a>
<a name="line-189"></a><a name="find"></a><span class='hs-comment'>-- | Move the focus to the specified element, if it is present.</span>
<a name="line-190"></a><span class='hs-comment'>--</span>
<a name="line-191"></a><span class='hs-comment'>-- Patch with much faster algorithm provided by Runar Bjarnason for version</span>
<a name="line-192"></a><span class='hs-comment'>-- 0.3.2. Improved again by Runar Bjarnason for version 0.3.3 to support</span>
<a name="line-193"></a><span class='hs-comment'>-- infinite lists on both sides of the focus.</span>
<a name="line-194"></a><span class='hs-definition'>find</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Eq</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-195"></a><span class='hs-definition'>find</span> <span class='hs-varid'>x</span> <span class='hs-varid'>pl</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>find'</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varop'>==</span><span class='hs-layout'>)</span> <span class='hs-varop'>.</span> <span class='hs-layout'>(</span><span class='hs-conid'>Label</span><span class='hs-varop'>.</span><span class='hs-varid'>get</span> <span class='hs-varid'>focus</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>positions</span> <span class='hs-varid'>pl</span>
<a name="line-196"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>find'</span> <span class='hs-varid'>pred</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-varid'>b</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span>
<a name="line-197"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>pred</span> <span class='hs-varid'>b</span> <span class='hs-keyword'>then</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>b</span>
<a name="line-198"></a> <span class='hs-keyword'>else</span> <span class='hs-conid'>List</span><span class='hs-varop'>.</span><span class='hs-varid'>find</span> <span class='hs-varid'>pred</span> <span class='hs-layout'>(</span><span class='hs-varid'>merge</span> <span class='hs-varid'>a</span> <span class='hs-varid'>c</span><span class='hs-layout'>)</span>
<a name="line-199"></a> <span class='hs-varid'>merge</span> <span class='hs-conid'>[]</span> <span class='hs-varid'>ys</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>ys</span>
<a name="line-200"></a> <span class='hs-varid'>merge</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-varid'>ys</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span> <span class='hs-conop'>:</span> <span class='hs-varid'>merge</span> <span class='hs-varid'>ys</span> <span class='hs-varid'>xs</span>
<a name="line-201"></a>
<a name="line-202"></a><a name="index"></a><span class='hs-comment'>-- | The index of the focus, leftmost is 0.</span>
<a name="line-203"></a><span class='hs-definition'>index</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Int</span>
<a name="line-204"></a><span class='hs-definition'>index</span> <span class='hs-layout'>(</span><span class='hs-conid'>PointedList</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Prelude</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>a</span>
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