README.md

   1 ---
   2 title: "Advent of Code 2020"
   3 output: html_document
   4 css: modest.css
   5 ---
   6 Code to solve the [Advent of Code](http://adventofcode.com/2020/) puzzles. This year, I'm using the puzzles to develop my skills in [Haskell](https://wiki.haskell.org/Haskell). I'm writing up a [commentary on these puzzles and my solutions](https://work.njae.me.uk/tag/advent-of-code/) on my blog.
   7
   8 [Learn you a Haskell](http://learnyouahaskell.com/chapters), [Introduction to Haskell 98](https://www.haskell.org/tutorial/index.html), and [Hackage](https://hackage.haskell.org/) are good resources.
   9
  10 The [Cabal user guide](https://cabal.readthedocs.io/en/latest/index.html) and [How I Start: Haskell](http://howistart.org/posts/haskell/1/) are good sources of using the tools.
  11
  12 # Toolchain
  13
  14 Install Ghcup following [the instructions](https://www.haskell.org/ghcup/install/#installation), making sure to load the updated environment with
  15
  16 ```bash
  17 source /home/neil/.ghcup/env
  18 ```
  19
  20 and then set the default GHC to use with `ghcup set ghc 9.0.1` .
  21
  22 Install [Haskell Language Server](https://haskell-language-server.readthedocs.io/en/latest/configuration.html) for Sublime Text
  23
  24
  25 ## Creating the repository and project
  26 Create the repository as normal: create the project in Gitolite, clone it, and insert the `.gitignore` and `README.md` files.
  27
  28 There's one package per day, with the code for each package in sub-directories of the root directory.
  29
  30 Create the basic `cabal` project.
  31
  32 ```
  33 cabal init
  34 ```
  35
  36 Modify the `advent-of-code21.cabal` file as needed, such as updating the Cabal version and writing the `common` stanzas.
  37
  38 ## Creating subsequent days
  39
  40 Each day lives in a separate directory, with code in the `src` directory.
  41
  42 Compile with
  43 ```
  44 cabal build
  45 ```
  46 or
  47 ```
  48 cabal build advent01
  49 ```
  50
  51 Run with
  52 ```
  53 cabal run advent01
  54 ```
  55
  56 If you want to pass in additional RTS parameters, do it like this:
  57 ```
  58 cabal run advent01 -- +RTS -K0 -RTS
  59 ```
  60
  61 Run interactively with
  62 ```
  63 cabal repl advent01
  64 ```
  65 or
  66 ```
  67 stack ghci advent01:exe:advent01
  68 ```
  69 if the first form is ambiguous.
  70
  71 To profile, use
  72
  73 ```
  74 cabal run advent01 --enable-profiling -- +RTS -N -p -s -hT
  75 ```
  76
  77 Or, you can simplify the RTS options by adding them to a new stanza in the cabal file:
  78
  79 ```
  80 executable advent01prof
  81   import: common-extensions, build-directives
  82   main-is: advent01/Main.hs
  83   build-depends: text, containers, linear, array, pqueue, mtl, lens
  84   ghc-options:         -O2
  85                        -Wall
  86                        -threaded
  87                        -rtsopts "-with-rtsopts=-N -p -s -hT"
  88 ```
  89
  90 then running
  91
  92 ```
  93 cabal run advent01prof --enable-profiling
  94 ```
  95
  96
  97 Generate the profile graph with
  98 ```
  99 hp2ps -M advent01.hp
 100 ```
 101
 102 For Cabal, look at [profiling with Cabal sandboxes](https://nikita-volkov.github.io/profiling-cabal-projects/)
 103
 104
 105 # Packages
 106
 107 Packages I used a lot:
 108
 109 * [Containers](https://hackage.haskell.org/package/containers) (and some [better documentation](https://haskell-containers.readthedocs.io/en/latest/intro.html)); [Unordered containers](https://hackage.haskell.org/package/unordered-containers) is a mostly-equivalent alternative.
 110 * [Attoparsec](https://hackage.haskell.org/package/attoparsec) (and [Megaparsec](https://hackage.haskell.org/package/megaparsec), and [ReadP](https://hackage.haskell.org/package/base-4.14.1.0/docs/Text-ParserCombinators-ReadP.html) once).
 111
 112 There are somewhat decent [tutorials on Megaparsec](https://markkarpov.com/tutorial/megaparsec.html) and [Attoparsec](https://www.schoolofhaskell.com/school/starting-with-haskell/libraries-and-frameworks/text-manipulation/attoparsec).
 113
 114 Packages I didn't use much, but need to remember:
 115
 116 * [Arithmoi](https://hackage.haskell.org/package/arithmoi) for number theory
 117 * [Pointed List](https://hackage.haskell.org/package/pointedlist-0.6.1) for zipper lists (sometimes circular)
 118 * [Vector](https://hackage.haskell.org/package/vector) for array-like things
 119 * [Linear](https://hackage.haskell.org/package/linear) for coordinate-vector like things
 120 * [Grid](https://hackage.haskell.org/package/grid) for 2-d grids
 121 * [Graph-wrapper](https://hackage.haskell.org/package/graph-wrapper) for graphs
 122 * [Lens](https://hackage.haskell.org/package/lens) (and a [summary of operators](https://github.com/ekmett/lens/wiki/Operators)). I didn't use these much this year, but did a lot last year.
 123 * [RWS](https://hackage.haskell.org/package/mtl-2.2.2/docs/Control-Monad-RWS-Lazy.html) (Reader-Writer-State monad stack); again, used a lot last year but not this year
 124 * [Monad loops](https://hackage.haskell.org/package/monad-loops-0.4.3/docs/Control-Monad-Loops.html), and [a description](https://conscientiousprogrammer.com/blog/2015/12/11/24-days-of-hackage-2015-day-11-monad-loops-avoiding-writing-recursive-functions-by-refactoring/)
 125 * [Replace-Megaparsec](https://github.com/jamesdbrock/replace-megaparsec), for using Mpc for all sorts of things traditionally done with regex substitutions.
 126
 127 # Readme
 128
 129 Build this readme file wth
 130 ```
 131 pandoc -s README.md > README.html
 132 ```
 133
 134 (Using the [Modest style](https://github.com/markdowncss/modest).)