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<title>src/Darcs/Witnesses/WZipper.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>-- Copyright (C) 2009 Florent Becker</span>
<a name="line-2"></a><span class='hs-comment'>--</span>
<a name="line-3"></a><span class='hs-comment'>-- This program is free software; you can redistribute it and/or modify</span>
<a name="line-4"></a><span class='hs-comment'>-- it under the terms of the GNU General Public License as published by</span>
<a name="line-5"></a><span class='hs-comment'>-- the Free Software Foundation; either version 2, or (at your option)</span>
<a name="line-6"></a><span class='hs-comment'>-- any later version.</span>
<a name="line-7"></a><span class='hs-comment'>--</span>
<a name="line-8"></a><span class='hs-comment'>-- This program is distributed in the hope that it will be useful,</span>
<a name="line-9"></a><span class='hs-comment'>-- but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="line-10"></a><span class='hs-comment'>-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<a name="line-11"></a><span class='hs-comment'>-- GNU General Public License for more details.</span>
<a name="line-12"></a><span class='hs-comment'>--</span>
<a name="line-13"></a><span class='hs-comment'>-- You should have received a copy of the GNU General Public License</span>
<a name="line-14"></a><span class='hs-comment'>-- along with this program; see the file COPYING. If not, write to</span>
<a name="line-15"></a><span class='hs-comment'>-- the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,</span>
<a name="line-16"></a><span class='hs-comment'>-- Boston, MA 02110-1301, USA.</span>
<a name="line-17"></a>
<a name="line-18"></a><span class='hs-comment'>{-# LANGUAGE CPP #-}</span>
<a name="line-19"></a>
<a name="line-20"></a><span class='hs-cpp'>#include "gadts.h"</span>
<a name="line-21"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Darcs</span><span class='hs-varop'>.</span><span class='hs-conid'>Witnesses</span><span class='hs-varop'>.</span><span class='hs-conid'>WZipper</span> <span class='hs-layout'>(</span> <span class='hs-conid'>FZipper</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>focus</span><span class='hs-layout'>,</span> <span class='hs-varid'>leftmost</span><span class='hs-layout'>,</span> <span class='hs-varid'>left</span>
<a name="line-22"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>rightmost</span><span class='hs-layout'>,</span> <span class='hs-varid'>right</span><span class='hs-layout'>,</span> <span class='hs-varid'>jokers</span><span class='hs-layout'>,</span> <span class='hs-varid'>clowns</span>
<a name="line-23"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>flToZipper</span><span class='hs-layout'>,</span> <span class='hs-varid'>lengthFZ</span><span class='hs-layout'>,</span> <span class='hs-varid'>nullFZ</span>
<a name="line-24"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>toEnd</span><span class='hs-layout'>,</span> <span class='hs-varid'>toStart</span>
<a name="line-25"></a> <span class='hs-layout'>)</span>
<a name="line-26"></a><span class='hs-keyword'>where</span>
<a name="line-27"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Darcs</span><span class='hs-varop'>.</span><span class='hs-conid'>Witnesses</span><span class='hs-varop'>.</span><span class='hs-conid'>Ordered</span> <span class='hs-layout'>(</span> <span class='hs-conid'>FL</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>RL</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>nullFL</span><span class='hs-layout'>,</span> <span class='hs-varid'>nullRL</span>
<a name="line-28"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>lengthFL</span><span class='hs-layout'>,</span> <span class='hs-varid'>lengthRL</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varop'>+<+</span><span class='hs-layout'>)</span>
<a name="line-29"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>reverseFL</span><span class='hs-layout'>,</span> <span class='hs-varid'>reverseRL</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-varop'>+>+</span><span class='hs-layout'>)</span>
<a name="line-30"></a> <span class='hs-layout'>)</span>
<a name="line-31"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Darcs</span><span class='hs-varop'>.</span><span class='hs-conid'>Witnesses</span><span class='hs-varop'>.</span><span class='hs-conid'>Sealed</span><span class='hs-layout'>(</span><span class='hs-conid'>Sealed2</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Sealed</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>FlippedSeal</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-32"></a>
<a name="line-33"></a><a name="FZipper"></a><span class='hs-comment'>-- forward zipper</span>
<a name="line-34"></a><a name="FZipper"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-35"></a> <span class='hs-conid'>FZipper</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>RL</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FL</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>y</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>z</span><span class='hs-layout'>)</span>
<a name="line-36"></a>
<a name="line-37"></a><a name="flToZipper"></a><span class='hs-comment'>-- Constructors</span>
<a name="line-38"></a><span class='hs-definition'>flToZipper</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FL</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-39"></a><span class='hs-definition'>flToZipper</span> <span class='hs-varid'>l</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FZipper</span> <span class='hs-conid'>NilRL</span> <span class='hs-varid'>l</span>
<a name="line-40"></a>
<a name="line-41"></a><span class='hs-varop'>--destructors</span>
<a name="line-42"></a><a name="nullFZ"></a><span class='hs-definition'>nullFZ</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-43"></a><span class='hs-definition'>nullFZ</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>nullRL</span> <span class='hs-varid'>l</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>nullFL</span> <span class='hs-varid'>r</span>
<a name="line-44"></a>
<a name="line-45"></a><a name="lengthFZ"></a><span class='hs-definition'>lengthFZ</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Int</span>
<a name="line-46"></a><span class='hs-definition'>lengthFZ</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lengthRL</span> <span class='hs-varid'>l</span> <span class='hs-varop'>+</span> <span class='hs-varid'>lengthFL</span> <span class='hs-varid'>r</span>
<a name="line-47"></a>
<a name="line-48"></a><a name="focus"></a><span class='hs-definition'>focus</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>Sealed2</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-49"></a><span class='hs-definition'>focus</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-conop'>:>:</span> <span class='hs-keyword'>_</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'>Sealed2</span> <span class='hs-varid'>x</span>
<a name="line-50"></a><span class='hs-definition'>focus</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-51"></a>
<a name="line-52"></a><a name="clowns"></a><span class='hs-comment'>-- | \"Clowns to the left of me, jokers to the right. Here I am, stuck</span>
<a name="line-53"></a><span class='hs-comment'>-- in the middle of you\"</span>
<a name="line-54"></a><span class='hs-comment'>-- <<a href="http://en.wikipedia.org/wiki/Stuck_in_the_Middle">http://en.wikipedia.org/wiki/Stuck_in_the_Middle</a>></span>
<a name="line-55"></a><span class='hs-definition'>clowns</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Sealed</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-conid'>RL</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-56"></a><span class='hs-definition'>clowns</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Sealed</span> <span class='hs-varid'>l</span>
<a name="line-57"></a>
<a name="line-58"></a><a name="jokers"></a><span class='hs-comment'>-- | See 'clowns'</span>
<a name="line-59"></a><span class='hs-definition'>jokers</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>a</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FlippedSeal</span> <span class='hs-layout'>(</span><span class='hs-conid'>FL</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-60"></a><span class='hs-definition'>jokers</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FlippedSeal</span> <span class='hs-varid'>r</span>
<a name="line-61"></a>
<a name="line-62"></a><a name="rightmost"></a><span class='hs-definition'>rightmost</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-63"></a><span class='hs-definition'>rightmost</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>NilFL</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>True</span>
<a name="line-64"></a><span class='hs-definition'>rightmost</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-65"></a>
<a name="line-66"></a><a name="right"></a><span class='hs-definition'>right</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-67"></a><span class='hs-definition'>right</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span><span class='hs-conop'>:>:</span><span class='hs-varid'>r</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FZipper</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span> <span class='hs-conop'>:<:</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span>
<a name="line-68"></a><span class='hs-definition'>right</span> <span class='hs-varid'>x</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>NilFL</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-69"></a>
<a name="line-70"></a><a name="leftmost"></a><span class='hs-definition'>leftmost</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Bool</span>
<a name="line-71"></a><span class='hs-definition'>leftmost</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-conid'>NilRL</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-72"></a><span class='hs-definition'>leftmost</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span>
<a name="line-73"></a>
<a name="line-74"></a><a name="left"></a><span class='hs-definition'>left</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-75"></a><span class='hs-definition'>left</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span> <span class='hs-conop'>:<:</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-layout'>(</span><span class='hs-varid'>b</span> <span class='hs-conop'>:>:</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
<a name="line-76"></a><span class='hs-definition'>left</span> <span class='hs-varid'>x</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-conid'>NilRL</span> <span class='hs-keyword'>_</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>x</span>
<a name="line-77"></a>
<a name="line-78"></a><a name="toEnd"></a><span class='hs-definition'>toEnd</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-79"></a><span class='hs-definition'>toEnd</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FZipper</span> <span class='hs-layout'>(</span><span class='hs-varid'>reverseFL</span> <span class='hs-varid'>r</span> <span class='hs-varop'>+<+</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-conid'>NilFL</span>
<a name="line-80"></a>
<a name="line-81"></a><a name="toStart"></a><span class='hs-definition'>toStart</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>FZipper</span> <span class='hs-varid'>p</span> <span class='hs-conid'>C</span><span class='hs-layout'>(</span><span class='hs-varid'>x</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-82"></a><span class='hs-definition'>toStart</span> <span class='hs-layout'>(</span><span class='hs-conid'>FZipper</span> <span class='hs-varid'>l</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FZipper</span> <span class='hs-conid'>NilRL</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>reverseRL</span> <span class='hs-varid'>l</span><span class='hs-layout'>)</span> <span class='hs-varop'>+>+</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span>
</pre></body>
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