Remove hint.html and index.html
As per discussions on GitHub the index.html and hint.html files should be deleted in favour of README.md files (from any .text/.txt/.markdown/.md files which will be turned into README.md in an upcoming commit).
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta name="GENERATOR" content="mkd2html 2.1.3 DL=DISCOUNT">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
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<link rel="stylesheet"
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type="text/css"
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href="../hint.css">
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<title>Best self documenting program</title>
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</head>
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<body>
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<h1>Best self documenting program</h1>
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<p>Hou Qiming<br>
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<a href="mailto:hqm03ster@gmail.com">hqm03ster@gmail.com</a></p>
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<h2>Judges' comments:</h2>
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<h3>To build:</h3>
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<pre><code>make hou
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</code></pre>
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<h3>To run:</h3>
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<pre><code>./hou 'a calculator expression -- see the C Code for details'
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</code></pre>
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<h3>Try:</h3>
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<pre><code>./hou 11/26+222/31
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./hou 'log((21701-19937)-(23209-21701))/log(2)'
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./hou 'sin(1.5708)+0.04321+log(sqrt(exp(1*1*1)))+(1+2*3)-0.4-0.6+(4+6)*(2-1+2*3)-tan(0.785398)+2*10/3*6*sqrt(16/2/2)*10+10000-1000'
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</code></pre>
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<h3>Selected Judges Remarks:</h3>
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<p>This self-documenting scientific calculator compiles clean with no
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warnings under the most strict pedantic mode of gcc and clang.</p>
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<p>The first example, along with the correct result appears in the
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source code. What does it mean?</p>
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<p>The calculator obeys the precendence rules and allows parenthesis,</p>
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<pre><code> ./hou '1+2*3'
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./hou '(1+2)*3'
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</code></pre>
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<p>What exactly does the text formatting do?</p>
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<p>What does this evaluate to in C?</p>
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<pre><code> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
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</code></pre>
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<h4>Self documenting source</h4>
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<p>Comments would almost be redundant. :-}</p>
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<h4>The ASCII art is valid C code</h4>
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<p>Not just fancy formatted comment removed by the C Pre-processor</p>
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<h4>The only multi-byte strings are format strings</h4>
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<p>The code does not contain some simple string-encoded lookup table for calculator operations.</p>
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<h4>Example input and output in the source</h4>
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<p>The example input and output in the C code is significant. Can you find out why?</p>
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<h4>The button layout</h4>
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<p>The button layout in the C code is significant … not just a nice looking layout.</p>
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<h4>input parsing</h4>
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<p>The parser is functionally equivalent to a normal arithmetic parser for all valid inputs.
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For another fun challenge: try to determine how it parses the command line argument.</p>
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<h2>Author’s comments:</h2>
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<h3>Obfuscations</h3>
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<p>This program is designed to be self-documenting. It doesn’t just provide an
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example command line. It also provides the expected output and illustrates all
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supported functionality using embedded ASCII art.</p>
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<ul>
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<li>A few line numbers are significant and careless beautification will break the program.</li>
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<li>The entire ASCII art is valid code. The preprocessor won’t remove any part of it.</li>
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<li>The only strings longer than 1 byte are printf/sscanf format strings, even
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after preprocessing. No string-encoded lookup table is used.</li>
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<li>The example input and its expected output are both algorithmically significant.</li>
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<li>The button layout is also significant.</li>
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<li>The actual syntax being parsed is not the obvious, despite being
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functionally equivalent for all correct inputs.</li>
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</ul>
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<h3>Portability</h3>
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<ul>
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<li>This program requires “argv” to point to writable memory. It doesn’t require
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the actual argv strings to be writable, though.</li>
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<li>This program requires ASCII.</li>
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<li>This program doesn’t work with %e style numbers like “1e-4”.</li>
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<li>Some seemingly redundant code works to eliminate warnings and evade a gcc bug.</li>
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</ul>
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<h3>Spoilers</h3>
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<p>The parser parses function names, substraction, and division as single-letter
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unary operators. A bitmask encoded hash table is used to check no-ops/digits
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and another hash function maps the ASCII to a function ordinal, which is then
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executed by the button panel.</p>
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<p>Both hash functions are found using a separate search program. Another program
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is used to find a way to format one hash function as example input such that
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it produces something resembling the bitmask hash table as part of its output.</p>
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<hr />
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<TABLE><TR>
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<TD><a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-sa/3.0/88x31.png" /></a></TD>
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<TD><P>© Copyright 1984-2012,
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<A HREF="/judges.html">Leo Broukhis, Simon Cooper, Landon Curt Noll</A>
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- All rights reserved<BR>
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This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.</P></TD>
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<TD> <!--<a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>--></TD>
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</TR></TABLE>
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</body>
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</html>
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