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  86 <header id="title-block-header">
  87 <h1 class="title">Advent of Code 2022</h1>
  88 </header>
  89 <p>Code to solve the <a href="http://adventofcode.com/2022/">Advent of Code</a> puzzles. This year, I’m using the puzzles to develop my skills in <a href="https://wiki.haskell.org/Haskell">Haskell</a>. I’m writing up a <a href="https://work.njae.me.uk/tag/advent-of-code/">commentary on these puzzles and my solutions</a> on my blog.</p>
  90 <p><a href="http://learnyouahaskell.com/chapters">Learn you a Haskell</a>, <a href="https://www.haskell.org/tutorial/index.html">Introduction to Haskell 98</a>, and <a href="https://hackage.haskell.org/">Hackage</a> are good resources.</p>
  91 <p>The <a href="https://cabal.readthedocs.io/en/latest/index.html">Cabal user guide</a> and <a href="http://howistart.org/posts/haskell/1/">How I Start: Haskell</a> are good sources of using the tools.</p>
  92 <h1 id="toolchain">Toolchain</h1>
  93 <p>Install Ghcup following <a href="https://www.haskell.org/ghcup/install/#installation">the instructions</a>, making sure to load the updated environment with</p>
  94 <div class="sourceCode" id="cb1"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="bu">source</span> /home/neil/.ghcup/env</span></code></pre></div>
  95 <p>and then set the default GHC to use with <code>ghcup set ghc 9.0.1</code> .</p>
  96 <p>Install <a href="https://haskell-language-server.readthedocs.io/en/latest/configuration.html">Haskell Language Server</a> for Sublime Text</p>
  97 <h2 id="creating-the-repository-and-project">Creating the repository and project</h2>
  98 <p>Create the repository as normal: create the project in Gitolite, clone it, and insert the <code>.gitignore</code> and <code>README.md</code> files.</p>
  99 <p>There’s one package per day, with the code for each package in sub-directories of the root directory.</p>
 100 <p>Create the basic <code>cabal</code> project.</p>
 101 <pre><code>cabal init</code></pre>
 102 <p>Modify the <code>advent-of-code21.cabal</code> file as needed, such as updating the Cabal version and writing the <code>common</code> stanzas.</p>
 103 <h2 id="creating-subsequent-days">Creating subsequent days</h2>
 104 <p>Each day lives in a separate directory, with code in the <code>src</code> directory.</p>
 105 <p>Compile with</p>
 106 <pre><code>cabal build</code></pre>
 107 <p>or</p>
 108 <pre><code>cabal build advent01</code></pre>
 109 <p>Run with</p>
 110 <pre><code>cabal run advent01</code></pre>
 111 <p>If you want to pass in additional RTS parameters, do it like this:</p>
 112 <pre><code>cabal run advent01 -- +RTS -K0 -RTS</code></pre>
 113 <p>Run interactively with</p>
 114 <pre><code>cabal repl advent01</code></pre>
 115 <p>or</p>
 116 <pre><code>stack ghci advent01:exe:advent01</code></pre>
 117 <p>if the first form is ambiguous.</p>
 118 <h2 id="profiling">Profiling</h2>
 119 <p>To profile, use</p>
 120 <pre><code>cabal run advent01 --enable-profiling -- +RTS -N -p -s -hT</code></pre>
 121 <p>Or, you can simplify the RTS options by adding them to a new stanza in the cabal file:</p>
 122 <pre><code>executable advent01prof
 123   import: common-extensions, build-directives
 124   main-is: advent01/Main.hs
 125   build-depends: text, containers, linear, array, pqueue, mtl, lens
 126   ghc-options:         -O2
 127                        -Wall
 128                        -threaded
 129                        -rtsopts &quot;-with-rtsopts=-N -p -s -hT&quot;</code></pre>
 130 <p>then running</p>
 131 <pre><code>cabal run advent01prof --enable-profiling</code></pre>
 132 <p>Generate the profile graph with</p>
 133 <pre><code>hp2ps -M advent01.hp</code></pre>
 134 <h1 id="packages">Packages</h1>
 135 <p>Packages I used a lot:</p>
 136 <ul>
 137 <li><a href="https://hackage.haskell.org/package/containers">Containers</a> (and some <a href="https://haskell-containers.readthedocs.io/en/latest/intro.html">better documentation</a>); <a href="https://hackage.haskell.org/package/unordered-containers">Unordered containers</a> is a mostly-equivalent alternative.</li>
 138 <li><a href="https://hackage.haskell.org/package/attoparsec">Attoparsec</a> (and <a href="https://hackage.haskell.org/package/megaparsec">Megaparsec</a>, and <a href="https://hackage.haskell.org/package/base-4.14.1.0/docs/Text-ParserCombinators-ReadP.html">ReadP</a> once).</li>
 139 </ul>
 140 <p>There are somewhat decent <a href="https://markkarpov.com/tutorial/megaparsec.html">tutorials on Megaparsec</a> and <a href="https://www.schoolofhaskell.com/school/starting-with-haskell/libraries-and-frameworks/text-manipulation/attoparsec">Attoparsec</a>.</p>
 141 <p>Packages I didn’t use much, but need to remember:</p>
 142 <ul>
 143 <li><a href="https://hackage.haskell.org/package/arithmoi">Arithmoi</a> for number theory</li>
 144 <li><a href="https://hackage.haskell.org/package/pointedlist-0.6.1">Pointed List</a> for zipper lists (sometimes circular)</li>
 145 <li><a href="https://hackage.haskell.org/package/vector">Vector</a> for array-like things</li>
 146 <li><a href="https://hackage.haskell.org/package/linear">Linear</a> for coordinate-vector like things</li>
 147 <li><a href="https://hackage.haskell.org/package/grid">Grid</a> for 2-d grids</li>
 148 <li><a href="https://hackage.haskell.org/package/graph-wrapper">Graph-wrapper</a> for graphs</li>
 149 <li><a href="https://hackage.haskell.org/package/lens">Lens</a> (and a <a href="https://github.com/ekmett/lens/wiki/Operators">summary of operators</a>). I didn’t use these much this year, but did a lot last year.</li>
 150 <li><a href="https://hackage.haskell.org/package/mtl-2.2.2/docs/Control-Monad-RWS-Lazy.html">RWS</a> (Reader-Writer-State monad stack); again, used a lot last year but not this year</li>
 151 <li><a href="https://hackage.haskell.org/package/monad-loops-0.4.3/docs/Control-Monad-Loops.html">Monad loops</a>, and <a href="https://conscientiousprogrammer.com/blog/2015/12/11/24-days-of-hackage-2015-day-11-monad-loops-avoiding-writing-recursive-functions-by-refactoring/">a description</a></li>
 152 <li><a href="https://github.com/jamesdbrock/replace-megaparsec">Replace-Megaparsec</a>, for using Mpc for all sorts of things traditionally done with regex substitutions.</li>
 153 </ul>
 154 <h1 id="readme">Readme</h1>
 155 <p>Build this readme file wth</p>
 156 <pre><code>pandoc -s README.md &gt; README.html</code></pre>
 157 <p>(Using the <a href="https://github.com/markdowncss/modest">Modest style</a>.)</p>
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