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<title>System/Console/Haskeline/Command/Undo.hs</title>
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<pre><a name="line-1"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Console</span><span class='hs-varop'>.</span><span class='hs-conid'>Haskeline</span><span class='hs-varop'>.</span><span class='hs-conid'>Command</span><span class='hs-varop'>.</span><span class='hs-conid'>Undo</span> <span class='hs-keyword'>where</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Console</span><span class='hs-varop'>.</span><span class='hs-conid'>Haskeline</span><span class='hs-varop'>.</span><span class='hs-conid'>Command</span>
<a name="line-4"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Console</span><span class='hs-varop'>.</span><span class='hs-conid'>Haskeline</span><span class='hs-varop'>.</span><span class='hs-conid'>LineState</span>
<a name="line-5"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>System</span><span class='hs-varop'>.</span><span class='hs-conid'>Console</span><span class='hs-varop'>.</span><span class='hs-conid'>Haskeline</span><span class='hs-varop'>.</span><span class='hs-conid'>Monads</span>
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<a name="line-7"></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-8"></a>
<a name="line-9"></a><a name="Undo"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>Undo</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span><span class='hs-layout'>,</span> <span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>InsertMode</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>}</span>
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<a name="line-11"></a><a name="UndoT"></a><span class='hs-keyword'>type</span> <span class='hs-conid'>UndoT</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>StateT</span> <span class='hs-conid'>Undo</span>
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<a name="line-13"></a><a name="runUndoT"></a><span class='hs-definition'>runUndoT</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Monad</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>UndoT</span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>m</span> <span class='hs-varid'>a</span>
<a name="line-14"></a><span class='hs-definition'>runUndoT</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>evalStateT'</span> <span class='hs-varid'>initialUndo</span>
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<a name="line-16"></a><a name="initialUndo"></a><span class='hs-definition'>initialUndo</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Undo</span>
<a name="line-17"></a><span class='hs-definition'>initialUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>emptyIM</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>,</span> <span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span><span class='hs-layout'>}</span>
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<a name="line-19"></a>
<a name="line-20"></a><a name="saveToUndo"></a><span class='hs-definition'>saveToUndo</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Save</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Undo</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Undo</span>
<a name="line-21"></a><span class='hs-definition'>saveToUndo</span> <span class='hs-varid'>s</span> <span class='hs-varid'>undo</span>
<a name="line-22"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>not</span> <span class='hs-varid'>isSame</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toSave</span><span class='hs-conop'>:</span><span class='hs-varid'>pastUndo</span> <span class='hs-varid'>undo</span><span class='hs-layout'>,</span><span class='hs-varid'>futureRedo</span><span class='hs-keyglyph'>=</span><span class='hs-conid'>[]</span><span class='hs-layout'>}</span>
<a name="line-23"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>undo</span>
<a name="line-24"></a> <span class='hs-keyword'>where</span>
<a name="line-25"></a> <span class='hs-varid'>toSave</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>save</span> <span class='hs-varid'>s</span>
<a name="line-26"></a> <span class='hs-varid'>isSame</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>pastUndo</span> <span class='hs-varid'>undo</span> <span class='hs-keyword'>of</span>
<a name="line-27"></a> <span class='hs-varid'>u</span><span class='hs-conop'>:</span><span class='hs-keyword'>_</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>u</span> <span class='hs-varop'>==</span> <span class='hs-varid'>toSave</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>True</span>
<a name="line-28"></a> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>False</span>
<a name="line-29"></a>
<a name="line-30"></a><a name="undoPast"></a><span class='hs-definition'>undoPast</span><span class='hs-layout'>,</span> <span class='hs-varid'>redoFuture</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Save</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=></span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Undo</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>s</span><span class='hs-layout'>,</span><span class='hs-conid'>Undo</span><span class='hs-layout'>)</span>
<a name="line-31"></a><span class='hs-definition'>undoPast</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>u</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>ls</span><span class='hs-layout'>,</span><span class='hs-varid'>u</span><span class='hs-layout'>)</span>
<a name="line-32"></a><span class='hs-definition'>undoPast</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>u</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>pastLS</span><span class='hs-conop'>:</span><span class='hs-varid'>lss</span><span class='hs-layout'>)</span><span class='hs-layout'>}</span>
<a name="line-33"></a> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>restore</span> <span class='hs-varid'>pastLS</span><span class='hs-layout'>,</span> <span class='hs-varid'>u</span> <span class='hs-layout'>{</span><span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lss</span><span class='hs-layout'>,</span> <span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>save</span> <span class='hs-varid'>ls</span> <span class='hs-conop'>:</span> <span class='hs-varid'>futureRedo</span> <span class='hs-varid'>u</span><span class='hs-layout'>}</span><span class='hs-layout'>)</span>
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<a name="line-35"></a><a name="redoFuture"></a><span class='hs-definition'>redoFuture</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>u</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>ls</span><span class='hs-layout'>,</span><span class='hs-varid'>u</span><span class='hs-layout'>)</span>
<a name="line-36"></a><span class='hs-definition'>redoFuture</span> <span class='hs-varid'>ls</span> <span class='hs-varid'>u</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>Undo</span> <span class='hs-layout'>{</span><span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>futureLS</span><span class='hs-conop'>:</span><span class='hs-varid'>lss</span><span class='hs-layout'>)</span><span class='hs-layout'>}</span>
<a name="line-37"></a> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>restore</span> <span class='hs-varid'>futureLS</span><span class='hs-layout'>,</span> <span class='hs-varid'>u</span> <span class='hs-layout'>{</span><span class='hs-varid'>futureRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lss</span><span class='hs-layout'>,</span> <span class='hs-varid'>pastUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>save</span> <span class='hs-varid'>ls</span> <span class='hs-conop'>:</span> <span class='hs-varid'>pastUndo</span> <span class='hs-varid'>u</span><span class='hs-layout'>}</span><span class='hs-layout'>)</span>
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<a name="line-40"></a>
<a name="line-41"></a><a name="saveForUndo"></a><span class='hs-definition'>saveForUndo</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Save</span> <span class='hs-varid'>s</span><span class='hs-layout'>,</span> <span class='hs-conid'>MonadState</span> <span class='hs-conid'>Undo</span> <span class='hs-varid'>m</span><span class='hs-layout'>)</span>
<a name="line-42"></a> <span class='hs-keyglyph'>=></span><span class='hs-conid'>Command</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s</span>
<a name="line-43"></a><span class='hs-definition'>saveForUndo</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-44"></a> <span class='hs-varid'>modify</span> <span class='hs-layout'>(</span><span class='hs-varid'>saveToUndo</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-45"></a> <span class='hs-varid'>return</span> <span class='hs-varid'>s</span>
<a name="line-46"></a>
<a name="line-47"></a><a name="commandUndo"></a><span class='hs-definition'>commandUndo</span><span class='hs-layout'>,</span> <span class='hs-varid'>commandRedo</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>MonadState</span> <span class='hs-conid'>Undo</span> <span class='hs-varid'>m</span><span class='hs-layout'>,</span> <span class='hs-conid'>Save</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=></span> <span class='hs-conid'>Command</span> <span class='hs-varid'>m</span> <span class='hs-varid'>s</span> <span class='hs-varid'>s</span>
<a name="line-48"></a><span class='hs-definition'>commandUndo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>simpleCommand</span> <span class='hs-varop'>$</span> <span class='hs-varid'>liftM</span> <span class='hs-conid'>Right</span> <span class='hs-varop'>.</span> <span class='hs-varid'>update</span> <span class='hs-varop'>.</span> <span class='hs-varid'>undoPast</span>
<a name="line-49"></a><a name="commandRedo"></a><span class='hs-definition'>commandRedo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>simpleCommand</span> <span class='hs-varop'>$</span> <span class='hs-varid'>liftM</span> <span class='hs-conid'>Right</span> <span class='hs-varop'>.</span> <span class='hs-varid'>update</span> <span class='hs-varop'>.</span> <span class='hs-varid'>redoFuture</span>
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