Typo fixes and change 'download entry source' to 'download entry' as it's the tarball, not the source itself. Rebuilt .entry.json and index.html files for all entries.
589 lines
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589 lines
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<!DOCTYPE html>
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<link rel="stylesheet" href="../../ioccc.css">
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
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<title>2005/anon - Best 3D puzzle</title>
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<meta name="description" content="2005 IOCCC entry anon - Best 3D puzzle">
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<meta name="keywords" content="IOCCC, 2005, IOCCC 2005, IOCCC entry, anon, Best 3D puzzle">
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<div class="header">
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<img src="../../png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
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<h1>The International Obfuscated C Code Contest</h1>
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<h2>2005/anon - Best 3D puzzle</h2>
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<div class="topnav">
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<a class="Left" href="../aidan/index.html">← aidan</a>
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<a class="Left" href="../index.html">↑ 2005 ↑</a>
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<a class="Left" href="../boutines/index.html">boutines →</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/2005/anon/anon.c">C code</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/2005/anon/Makefile">Makefile</a>
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<a class="Right" href="#inventory">Inventory</a>
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<a href="../../bugs.html">Bugs & (mis)features</a>
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<a href="../../faq.html#fix_an_entry">Fixing IOCCC entries</a>
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<a href="../../faq.html#fix_web_site">Fixing the web site</a>
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<a href="../../faq.html#fix_author">Fixing author info</a>
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<div class="sidenav">
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<a href="../../judges.html">The IOCCC Judges</a>
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<a href="../../contact.html">Contacting the IOCCC</a>
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<h2 id="author"><a name="author"></a>Author:</h2>
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<ul>
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<li>Name: <a href="../../authors.html#Anonymous_2005">Anonymous 2005</a><br>
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Location: <a href="../../location.html#ZZ">ZZ</a> - <em>Unknown location</em>
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<br><br></li>
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<h2 id="to-build">To build:</h2>
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<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span></span></code></pre></div>
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<p>NOTE: there is an alternate version for vi(m) like movements. See <a href="#alternate-code">alternate
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version</a> below. If your terminal has problems with the
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<code>stty(1)</code> commands try:</p>
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<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> anon-no_stty</span></code></pre></div>
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<p>This will compile <a href="anon.c">anon.c</a> as <code>anon</code> to not use <code>stty(1)</code>.</p>
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<h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
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<p>The current status of this entry is:</p>
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<pre><code>STATUS: INABIAF - please **DO NOT** fix</code></pre>
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<p>For more detailed information see <a href="../../bugs.html#2005_anon">2005 anon bugs</a>.</p>
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<h2 id="to-use">To use:</h2>
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<div class="sourceCode" id="cb4"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./anon</span> x y <span class="pp">[</span><span class="ss">z</span><span class="pp">]</span></span></code></pre></div>
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<h2 id="try">Try:</h2>
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<div class="sourceCode" id="cb5"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./anon</span> 4 4</span>
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<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a></span>
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<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a><span class="ex">./anon</span> 3 3 3</span></code></pre></div>
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<p>After a very large number of moves this program will deliberately force itself
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to destroy its runtime stack. This is the author’s way to prevent you from being
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frustrated (which might happen as it likes to create unsolvable puzzles just to
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hook you) and spending too much time playing. :-)</p>
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<p>If you want to see this in action you can easily do this:</p>
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<div class="sourceCode" id="cb6"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="fu">yes</span> <span class="st">'please crash on me :-)'</span> <span class="kw">|</span> <span class="ex">./anon</span> 4 4</span></code></pre></div>
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<p>What happens if you specify a larger board? For instance:</p>
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<div class="sourceCode" id="cb7"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="fu">yes</span> <span class="st">'please crash on me :-)'</span> <span class="kw">|</span> <span class="ex">./anon</span> 10 10 10</span></code></pre></div>
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<p>If you specify more than three args the program might also crash or do
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something strange. This might also happen if you specify excessively large board
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dimensions. Try <code>100 100 100</code> for instance and see what happens!</p>
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<h2 id="alternate-version">Alternate version:</h2>
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<p>The alternate version uses <code>vi(m)</code> like movement keys.</p>
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<h3 id="alternate-build">Alternate build:</h3>
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<div class="sourceCode" id="cb8"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> alt</span></code></pre></div>
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<p>To compile the version without <code>stty(1)</code>:</p>
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<div class="sourceCode" id="cb9"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span> alt-no_stty</span></code></pre></div>
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<h3 id="alternate-use">Alternate use:</h3>
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<p>Use <code>anon.alt</code> as you would <code>anon</code> with the change in movements:</p>
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<pre><code>k | Move empty spot up
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h | Move empty spot left
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j | Move empty spot down
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l | Move empty spot right
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J | Move empty spot forwards
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K | Move empty spot backwards</code></pre>
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<h2 id="judges-remarks">Judges’ remarks:</h2>
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<p>Taking the 4x4 board with 15 tiles to a whole new level, this entry takes this
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puzzle to a whole new dimension! While you puzzle out this puzzle, we invite
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you to take a good LONG look how and WHY <code>main()</code> is recursively called and how
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the runtime stack is used.</p>
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<h2 id="authors-remarks">Author’s remarks:</h2>
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<h3 id="about-the-game-itself">ABOUT THE GAME ITSELF</h3>
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<p>Remember Sam Loyd’s <a href="https://en.wikipedia.org/wiki/15_puzzle">Fifteen Puzzle</a>?
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It consists of a 4x4 board with 15 tiles numbered 1 to 15, and an empty spot.
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The goal of the game is to slide the tiles around without lifting them off the
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board, so that they become sorted.</p>
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<p>Well, that was then. This program is the 21st century version of the Fifteen
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Puzzle: not only does it allow arbitrary board sizes, it also supports <em>3D</em>
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boards! The tiles are numbered from 1 to N, where N is one less the number of
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spaces on the board, and the goal is to rearrange them so that they appear
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sorted in the order they appear on the screen.</p>
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<p>The program takes 2 or 3 arguments, specifying the dimensions of the board.
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For example, to play the original version of the Fifteen Puzzle:</p>
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<div class="sourceCode" id="cb11"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./anon</span> 4 4</span></code></pre></div>
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<p>To play with a 3D board, do something like this:</p>
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<div class="sourceCode" id="cb12"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./anon</span> 3 3 3</span></code></pre></div>
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<p><strong>WARNING: do NOT run the program with more than 3 command-line arguments.
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This will trigger a bug that will cause it to crash or do something strange.
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:-)</strong></p>
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<p>Also, resist the temptation to create very large puzzles. The program does not
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attempt to resize your terminal for you, and will produce confusing output. It
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may also crash on you if you insist on running it with excessively large board
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dimensions. :-) (10x10x10 is considered a safe upper limit.)</p>
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<p>The empty space on the board is represented by a space filled with <code>#</code>
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characters instead of digits. To slide the tiles around, use the following
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keys:</p>
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<pre><code>i | Slide the tile above the current empty space downwards.
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j | Slide the tile to the left of the current empty space to the right.
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k | Slide the tile below the current empty space upwards.
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l | Slide the tile to the right of the current empty space to the left.
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o | Slide the tile behind the current empty space forwards.
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n | Slide the tile in front of the current empty space backwards.</code></pre>
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<p>To quit the game:</p>
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<pre><code>q | Quit the game.</code></pre>
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<p>Note that, for example, sliding the tile above the current empty spot
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downwards will fill up the empty spot, and create a new empty spot above where
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the current empty spot was. Hence, you could think of the movement keys in
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terms of how they effectively “move” the empty spot:</p>
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<pre><code>i | Move empty spot up
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j | Move empty spot left
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k | Move empty spot down
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l | Move empty spot right
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n | Move empty spot forwards
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o | Move empty spot backwards</code></pre>
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<p><strong>NOTE:</strong> as a measure of alleviating counter-productivity due to addiction to
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this game, particularly for those hardcore gamers who insist on solving a
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10x10x10 puzzle during work hours, and also to give an upper bound to user
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frustration when the program generates an unsolvable puzzle (which it does
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roughly half the time, just to hook you), the program will, after a very large
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number of moves (which is system-specific) terminate itself by forcefully
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destroying its own runtime stack. This will result in a core dump and/or an
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abnormal termination message; but this is a feature, not a bug! :-)</p>
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<h3 id="compile-notes">COMPILE NOTES</h3>
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<p>This program complies with ANSI/C99. It uses ANSI terminal control sequences,
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and so requires a terminal that understands ANSI sequences, such as VT100 or
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xterm.</p>
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<p>Some compilers may emit lots of warnings about how things ought to be
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parenthesized (e.g. <code>gcc -Wall</code>). This is deliberate, since if everything were
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parenthesized “properly” the program would fail to work. It (ab)uses C
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operator precedence to accomplish some cool hacks. :-) However, there are no
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compiler errors. I have tested this with <code>gcc -pedantic -std=c99</code>.</p>
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<p>The program also uses <code>stty cbreak</code>. If this breaks on your system, compile it
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with <code>-DNO_STTY</code>. The game interface will be a bit annoying (you will need to
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hit enter after every key), but it works.</p>
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<p>The game requires lots of space on the runtime stack space due to deep
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recursion, among other things. :-)</p>
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<p>See spoilers below for more notes about portability.</p>
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<h3 id="about-the-code">ABOUT THE CODE</h3>
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<p>Clearly, the author is very, very confused. Although he has broken up the file
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into sections labelled with helpful headings, and although he has left ample
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whitespace between all those <code>#define</code>s to make them easier to read, :-) and
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although he has helpfully formatted the code with beautiful indentation,
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something is clearly very, very wrong.</p>
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<p>In fact, the closer you look at this code, the more you realize something is
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horribly wrong with it. For example, why is it that the first statement in
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<code>main()</code> is a <code>return</code>? What do all those nested <code>do</code> loops do (pun intended)? Why
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is the first statement inside the first <code>do</code> loop a mere integer literal? Why
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are there such strange statements, like that empty string on line 65, or that
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isolated <code>||</code> on line 68?</p>
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<p>But wait… why aren’t any statements terminated by semicolons? Why is there
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only ONE semicolon in the entire program?! Why is the author opening nested
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blocks by such strange things as <code>||</code> and <code>(</code>, and closing them by <code>||</code> and <code>))</code>? The
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<code>for</code> loop isn’t a <code>for</code> loop! The <code>do</code> loop isn’t a <code>do</code> loop! Or… are they? Well,
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the <code>for</code> loop is defined in terms of a <code>while</code> loop. But wait, the <code>while</code> loop is
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defined in terms of the <code>do</code> loop. And the <code>do</code> loop is defined in terms of …
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Huh???</p>
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<p>And that <code>switch</code> statement toward the end of the program… wait a minute,
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that’s not a <code>switch</code> statement! Why is a <code>case</code> defined in terms of a <code>switch</code>
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statement?! And that initial return isn’t a return! Well, it is… but not what
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you might think!</p>
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<p>Let’s see if it all makes sense after we run it through CPP…</p>
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<p>Uh oh. The result looks like the diseased imagination of a mind more confused
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than the one who wrote the original code. Unfortunately, unless you’re a Lisp
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expert, it is probably easier to understand the program in its original form.
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(And even then.) But that’s just so, so wrong…</p>
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<p>The entire program consists of a single expression, returned from <code>main()</code>.
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There are no <code>if</code> statements, no <code>for</code> loops or any looping or control constructs
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besides the <code>return</code>, in spite of the misleading appearance of the original
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source. :) Yes I know, this has been attempted before, using <code>?:</code> and the bad
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old comma operator. BUT this program does NOT use the <code>?:</code> operator, and there
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are only TWO comma operators in the entire program–and they are only there
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because <code>srand()</code> and <code>exit()</code> return void.</p>
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<p>The entire program consists of a single boolean expression returned from
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<code>main()</code>. Looping is achieved by recursion, of course, and branching is achieved
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by exploiting short-circuit evaluation of boolean expressions. :-)</p>
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<p>But this is not all.</p>
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<p>It is comprehensible that the program can achieve branching and looping using
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only boolean expressions and recursion. But HOW does the program STORE DATA???
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There are no variables of any kind in the program except for the two arguments
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to <code>main()</code>. There are certainly no arrays declared anywhere. The program does
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not call any memory allocation routines, nor any function that indirectly
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returns allocated memory. Yet it happily looks up array references without
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crashing. How??</p>
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<p>One might be tempted to think that this program would be highly non-portable
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because of such insane hacks. However, it has been tested and proven to work
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on the following architectures:</p>
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<ul>
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<li>i386/linux</li>
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<li>sparc/solaris</li>
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<li>parisc64/linux</li>
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<li>arm/linux</li>
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<li>s390/linux</li>
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<li>mips/linux</li>
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<li>m68k/linux</li>
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<li>ia64/linux</li>
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<li>sparc64/linux</li>
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</ul>
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<p>It probably will also compile and work on many (all?) other *nix platforms as
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well. How does it achieve this incredible feat?</p>
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<h3 id="spoiler">SPOILER</h3>
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<p>Read the following only if you give up figuring it out :-)</p>
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<h4 id="the-evil-hack">The Evil Hack</h4>
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<p>The program (ab)uses an implicit assumption underlying practically all
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architectures, and that is that parameters to C functions are implicit local
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variables allocated on the runtime stack. This runtime stack is a contiguous
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section of memory, and therefore, after <code>N</code> recursive calls of <code>main()</code> to
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itself, there is enough room on the stack to store whatever the program desires,
|
||
so long as it does not exceed the maximum stack size.</p>
|
||
<p>(Theoretically, the runtime stack doesn’t <strong>have</strong> to be contiguous… but all
|
||
current architectures that are worth consideration make this assumption. I
|
||
submit that this implies this program is 100% portable, even though
|
||
theoretically it shouldn’t even work in the first place.) :-)</p>
|
||
<p>There are two types of architectures the program must handle: those that
|
||
allocate the stack top-down, and those that allocate the stack bottom-up. The
|
||
program correctly detects this at runtime, and adjusts itself accordingly.
|
||
:-) (It is a simple matter of testing if the address of <code>argc</code> in a recursive
|
||
call is greater or less than in the parent call.)</p>
|
||
<p>To avoid having to handle issues of <code>int</code> sizes, memory alignment, what exactly
|
||
is on the stack between successive locations of <code>argc</code>, etc., the program
|
||
(ab)uses the fact that <code>argc</code> must necessarily be allocated on an aligned
|
||
address, and therefore, the range of memory between two <code>argc</code>s is aligned, and
|
||
therefore safe to use as an array of <code>long</code>s.[*] The program also compares the
|
||
pointers as <code>long*</code> pointers, so that it will not have to deal with mapping
|
||
bytes to larger types. The initial memory allocation is done by recursively
|
||
calling <code>main()</code> until there is enough space on the stack (the exact number of
|
||
recursive calls is, of course, architecture-dependent).</p>
|
||
<p>[*] <code>long</code> was chosen instead of <code>int</code>, in order to skirt around pointer-size
|
||
issues on architectures like ia64. It really can be made anything large enough
|
||
to hold both <code>int</code>s and pointers. <code>:-)</code></p>
|
||
<p>After the stack is deemed to have grown deep enough to be a sufficiently <code>long</code>
|
||
array (pun intended), the program begins its real code. It uses <code>argc</code> to keep
|
||
track of what it’s supposed to be doing (since <code>main()</code> is the only function),
|
||
and <code>argv</code> to point to the base of this array (which is computed differently
|
||
based on how the architecture allocates the stack). Since this fills up the
|
||
only two variables in the program, everything else is stored in the <code>MASS</code> [**]
|
||
array.</p>
|
||
<p>[**] for “Memory Allocated by Stack Smashing” :-)</p>
|
||
<p>Note that from this point on, all bets are off as to what the contents of the
|
||
runtime stack are below the current recursive call to <code>main()</code>. We are
|
||
overwriting frame pointers, return addresses, etc., with data. Hence, the
|
||
program must never return from this call, otherwise it will crash horribly.
|
||
That’s why I had to call <code>exit()</code> even though it meant I can no longer claim the
|
||
program doesn’t need the comma operator. :-) (I was going to skirt around the
|
||
issue by indirectly calling <code>exit()</code>, such as via <code>bsearch()</code> or <code>raise()</code>, but I
|
||
was getting too close to the size limit.)</p>
|
||
<h4 id="some-notes-about-the-macros">Some notes about the macros</h4>
|
||
<p>In spite of the frightening appearance, it is probably easiest to understand
|
||
the code in its original form. (Don’t even try running <code>indent</code> on it: on my
|
||
system it chokes and complains about nesting errors.)</p>
|
||
<p>Most of the <code>#define</code>s are just to keep the code size down, due to the abusive
|
||
amounts of type casting employed. The others define a bizarre “programming
|
||
language” (in the crudest, most twisted sense of the word) that the author
|
||
used to write this mess.</p>
|
||
<p><code>R(i)</code> and <code>W(i,j)</code> are macros to read/write the <code>i</code>th position of the <code>MASS</code>.</p>
|
||
<p><code>A(i)</code> retrieves the <code>i</code>th command-line argument. This is slightly tricky,
|
||
because by the time the <code>MASS</code> is setup, we no longer have access to the
|
||
original values of <code>argc</code> and <code>argv</code>. So what is done is that the initial memory
|
||
allocation code will save <code>argc</code> and <code>argv</code> into positions 8 and 9 in the <code>MASS</code>
|
||
after the allocation. It does this by using <code>argv</code>, which at that time contains
|
||
a pointer to the top-level <code>argc</code>, to compute the location of the top-level
|
||
<code>argv</code>. This is done before the rest of the <code>MASS</code> is used, since otherwise they
|
||
may be overwritten.</p>
|
||
<p><code>do(x,y)</code> has nothing to do with <code>do</code> loops. :-) It defines a “state” in <code>main()</code>,
|
||
essentially, what to do when <code>main()</code> is called with <code>argc</code> containing a
|
||
particular value. (This is why the user must never run the program with more
|
||
than 3 arguments. :-) The state number is <code>x</code>, and <code>y</code> is the code. The program’s
|
||
boolean expression consists of a number of states <code>&&</code>d together. Within each
|
||
state, it is assumed that statements are separated by <code>||</code>. All statements are
|
||
assumed to evaluate to false. This makes it easy to write conditional
|
||
statements: <code>if (a) { b } ...</code> can simply be written <code>a && b || ...</code>. All
|
||
states created by <code>do(x,y)</code> are assumed to evaluate to false. There is only 1
|
||
state which can return true or false: state 5, a “manually-implemented” state
|
||
which determines whether the system uses top-down or bottom-up stack
|
||
allocation. It’s the only state that needs to return a value from the boolean
|
||
expression, since once the <code>MASS</code> is initialized any return value can simply be
|
||
stored in a well-known location in the <code>MASS</code>.</p>
|
||
<p><code>if(p,q,r,s)</code> is, in fact, an <code>if</code> statement. :-) It is equivalent to:</p>
|
||
<div class="sourceCode" id="cb16"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb16-1"><a href="#cb16-1" aria-hidden="true" tabindex="-1"></a><span class="cf">if</span> <span class="op">(</span>p<span class="op">)</span> <span class="op">{</span> q<span class="op">;</span> r <span class="op">}</span> <span class="cf">else</span> <span class="op">{</span>s<span class="op">}</span></span></code></pre></div>
|
||
<p>Why are <code>q</code> and <code>r</code> split up? Because it’s cleaner (in whatever twisted sense of
|
||
the word that can be applied to an IOCCC entry) to implement using boolean
|
||
expressions. Keep in mind that all statements are assumed to evaluate to
|
||
false. The proof that this macro in fact implements an <code>if-then-else</code> construct
|
||
is left as an exercise for the reader.</p>
|
||
<p><code>while(x,y,z)</code> is actually a <code>while</code> loop after all. :-) It implements the loop
|
||
using, of course, recursive calls to <code>main()</code>. However, this macro doesn’t
|
||
actually run a <code>while</code> loop; it implements the loop in the state numbered <code>x</code>. It
|
||
is used for defining a <code>while</code> loop, which can then be called from another state
|
||
using <code>f(x)</code>. (The reason we can’t directly implement a <code>while</code> loop inside
|
||
another state ought to be clear: we can’t recursively call <code>main()</code> to enter
|
||
into the middle of a state.)</p>
|
||
<p>However, it <em>is</em> possible to implement a <code>for</code> loop directly inside a state! The
|
||
<code>for(s,i,x,y,z,Z)</code> macro does exactly this. Well, actually, technically speaking
|
||
this macro can only be used as the last thing in a state, because it secretly
|
||
closes the current state and opens a new one behind the programmer’s back.
|
||
:-) Its intended usage is this: <code>s</code> is the state number for the loop body, and
|
||
<code>i</code> is the index variable (well, the index into the <code>MASS</code> of the index
|
||
variable); <code>x</code> and <code>y-1</code> define the starting and ending values of <code>i</code>, and <code>z</code>
|
||
is the loop body. <code>Z</code> is the post-loop code in the current state. For example:</p>
|
||
<div class="sourceCode" id="cb17"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb17-1"><a href="#cb17-1" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span><span class="op">(</span>s<span class="op">,</span>i<span class="op">,</span> <span class="dv">0</span><span class="op">,</span> <span class="dv">10</span><span class="op">,</span></span>
|
||
<span id="cb17-2"><a href="#cb17-2" aria-hidden="true" tabindex="-1"></a>some_code <span class="op">,</span></span>
|
||
<span id="cb17-3"><a href="#cb17-3" aria-hidden="true" tabindex="-1"></a>other_code<span class="op">)</span></span></code></pre></div>
|
||
<p>is equivalent to:</p>
|
||
<div class="sourceCode" id="cb18"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb18-1"><a href="#cb18-1" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span> <span class="op">(</span>i<span class="op">=</span><span class="dv">0</span><span class="op">;</span> i<span class="op">&</span>lt<span class="op">;</span><span class="dv">10</span><span class="op">;</span> i<span class="op">++)</span> <span class="op">{</span></span>
|
||
<span id="cb18-2"><a href="#cb18-2" aria-hidden="true" tabindex="-1"></a> some_code<span class="op">;</span></span>
|
||
<span id="cb18-3"><a href="#cb18-3" aria-hidden="true" tabindex="-1"></a><span class="op">}</span></span>
|
||
<span id="cb18-4"><a href="#cb18-4" aria-hidden="true" tabindex="-1"></a>other_code<span class="op">;</span></span></code></pre></div>
|
||
<p>Note the “wrong” indentation in the former: the author prefers to write it
|
||
that way, since the analogy to the usual <code>for</code> loop is clearer. This is why it’s
|
||
easier to understand the pre-CPP code, since after CPP, the macro reshuffles
|
||
<code>some_code</code> after <code>other_code</code> so that it can close the current state and define
|
||
the one containing the loop body. (Have I told you that the author of this
|
||
program is horribly, horribly, confused? :-) This confusion also shows up in
|
||
the superficial appearance of the program, which heavily suffers from wrong
|
||
indentation.)</p>
|
||
<p>In spite of all appearances, <code>switch()</code> really is just a shorthand macro for
|
||
reducing code size. The evil choice of macro name is just to instill more
|
||
confusion into the would-be decipherer of this entry. :-) After all, <code>case()</code>
|
||
really <em>is</em> the equivalent of a <code>case</code> statement, implemented using <code>&&</code>, and
|
||
conveniently encapsulating code common to the cases in the only <code>switch</code>
|
||
statement in the program, which is the code that decides what to do with a
|
||
key press. What could be more fun than to define such a case in terms of a
|
||
<code>switch</code>? :-)</p>
|
||
<p>Finally, for those who give up deciphering this horribly confused code, here
|
||
are the mappings of various locations of the <code>MASS</code> to their usage in the
|
||
program, and what the various state numbers are meant to do:</p>
|
||
<h4 id="mass-usage-map">MASS usage map</h4>
|
||
<pre><code>0 | Function return value
|
||
1 | Function argument 1
|
||
2 | Function argument 2
|
||
3 | Function argument 3
|
||
4 | Scratch register 1
|
||
5 | Scratch register 2
|
||
6 | Scratch register 3
|
||
7 | Scratch register 4
|
||
8 | Value of original argv :-)
|
||
9 | Value of original argc :-)
|
||
11 | Zero register (always set to 0)
|
||
12 | Width of board
|
||
13 | Length of board
|
||
14 | Height of board
|
||
15 | Current position of hole
|
||
16 | Random seed for rand_r(3)
|
||
18 | Scratch register used by state 18 :-)
|
||
31 | field width for printing tiles
|
||
32 | Start of board data</code></pre>
|
||
<p>(<strong>CAVEAT:</strong> not all of these mappings ended up in the final version of the
|
||
program, mainly due to size limitations which entailed the trimming off of a
|
||
lot of neat features in the game. It is left as an exercise for the reader to
|
||
figure out which of these are actually used.)</p>
|
||
<p>Note that <code>argv</code> and <code>argc</code> necessarily need to stay away from lower indices of
|
||
the <code>MASS</code>, because otherwise they may overwrite their original values when the
|
||
memory allocation code saves them. Index 8 is deemed “safe enough”. (It seems
|
||
to be on all tested architectures.)</p>
|
||
<h4 id="state-number-assignments">State number assignments</h4>
|
||
<pre><code>1 | showhelp
|
||
2 | showhelp
|
||
3 | is 2D: start init
|
||
4 | is 3D: start init
|
||
5 | find allocation type
|
||
6 | MASS init, bottom-up
|
||
7 | MASS init, top-down
|
||
8 | main program
|
||
9 | generate() outer loop
|
||
13 | render()
|
||
14 | render() loop
|
||
15 | exit(0)
|
||
16 | pick a tile that hasn't occurred yet
|
||
17 | inner loop of 16.
|
||
18 | main loop
|
||
19 | checkwin() loop</code></pre>
|
||
<p>Note that some of the manually-implemented states (those not implemented by
|
||
<code>do()</code>) respond to multiple state numbers. Also note that states 1-4
|
||
conveniently correspond to what the program should do when 1-4 arguments are
|
||
given at the command-line. :-)</p>
|
||
<p>The original intention was to include a parity-checking routine in the game so
|
||
that it will always generate a solvable game. However, size limits
|
||
necessitated the removal of this code. And besides, the game is more addictive
|
||
when it’s sometimes unsolvable. Especially when it taunts the user with a
|
||
smiley. :-)</p>
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
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||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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|
||
For more information, see:
|
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|
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|
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|
||
|
||
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|
||
|
||
<h1 id="inventory-for-2005anon"><a name="inventory"></a>Inventory for 2005/anon</h1>
|
||
<p><a href="#top">Jump to top</a></p>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/anon.c">anon.c</a> - entry source</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/Makefile">Makefile</a> - entry Makefile</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/anon.alt.c">anon.alt.c</a> - alternative source</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/anon.orig.c">anon.orig.c</a> - original source</li>
|
||
<li><a href="2005_anon.tar.bz2">2005_anon.tar.bz2</a> - download entry</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a href="index.html">index.html</a> - entry home page</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/README.md">README.md</a> - markdown source for index.html</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/.entry.json">.entry.json</a> - description of entry in JSON</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2005/anon/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
|
||
<li><a href=".path">.path</a> - directory path from top directory</li>
|
||
</ul>
|
||
|
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|
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|
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<!--
|
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|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
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|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
|
||
<div class="footer">
|
||
<h2>Copyright and CC BY-SA 4.0 License</h2>
|
||
<p>This file and web page is:</p>
|
||
<blockquote><b>Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.</b></p></blockquote>
|
||
<p>You are free to share and adapt this file under the terms of this license:</p>
|
||
<blockquote><b>Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)</b></blockquote>
|
||
<p>For more information, see:</p>
|
||
<blockquote><a
|
||
href="https://creativecommons.org/licenses/by-sa/4.0/">https://creativecommons.org/licenses/by-sa/4.0/</a></blockquote>
|
||
<h2>Coda</h2>
|
||
<p><a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2005%2Fanon%2Findex.html">Nu HTML check this web page</a></p>
|
||
<p><a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a></p>
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