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 [Stack documentation](https://docs.haskellstack.org/en/stable/README/) and [How I Start: Haskell](http://howistart.org/posts/haskell/1/) are good sources of using the tools.
  11
  12
  13 # Toolchain
  14
  15 I'm using the basic Haskell Platform installation, together with `stack` to manage the packages and dependencies (install with
  16 ```
  17 $ sudo aptitude install haskell-platform haskell-stack
  18 ```
  19 ), then updgrade with
  20 ```
  21  stack upgrade --binary-only
  22 ```
  23 as the version in the Ubuntu repos is too old to work with current Haskell Stack package sets.
  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 `stack` project. This will create a new directory. Note that this new directory name can't have a hyphen-delimited word that's just digits, so the project will have to be `advent-of-code`
  31
  32 ```
  33 stack new advent-of-code --bare simple
  34 ```
  35
  36 Modify the `stack.yaml` file as needed, such as adding the `ghc-options` stanza.
  37
  38 ## Creating subsequent days
  39
  40 Each day lives in a separate directory, with its own `package.yaml` file and code in the `src` directory. (I based this configuration from [mstksg's setup](https://github.com/mstksg/advent-of-code-2018).)
  41
  42 Compile with
  43 ```
  44 stack build
  45 ```
  46 or
  47 ```
  48 stack build advent01
  49 ```
  50
  51 Run with
  52 ```
  53 stack exec advent01
  54 ```
  55
  56 If you want to pass in additional RTS parameters, do it like this:
  57 ```
  58 stack exec -- advent01 +RTS -K0 -RTS
  59 ```
  60
  61 Run interactively with
  62 ```
  63 stack ghci 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 stack build --executable-profiling --library-profiling --ghc-options="-fprof-auto -rtsopts" advent01
  74 ```
  75 then run with
  76 ```
  77 stack exec --profile -- advent01 +RTS -p -hy
  78 ```
  79 Generate the profile graph with
  80 ```
  81 stack exec hp2ps advent01.hp
  82 ```
  83
  84 # Packages
  85
  86 Stack is using the [14.16-lts resolver](https://www.stackage.org/lts-16.25) for packages, so make sure you read the [correct documentation for the packages included in it](https://www.stackage.org/lts-16.25/docs).
  87
  88 Packages I used a lot:
  89
  90 * [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.
  91 * [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).
  92
  93 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).
  94
  95 Packages I didn't use much, but need to remember:
  96
  97 * [Arithmoi](https://hackage.haskell.org/package/arithmoi) for number theory
  98 * [Pointed List](https://hackage.haskell.org/package/pointedlist-0.6.1) for zipper lists (sometimes circular)
  99 * [Vector](https://hackage.haskell.org/package/vector) for array-like things
 100 * [Linear](https://hackage.haskell.org/package/linear) for coordinate-vector like things
 101 * [Grid](https://hackage.haskell.org/package/grid) for 2-d grids
 102 * [Graph-wrapper](https://hackage.haskell.org/package/graph-wrapper) for graphs
 103 * [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.
 104 * [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
 105 * [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/)
 106 * [Replace-Megaparsec](https://github.com/jamesdbrock/replace-megaparsec), for using Mpc for all sorts of things traditionally done with regex substitutions.
 107
 108 # Readme
 109
 110 Build this readme file wth
 111 ```
 112 pandoc -s README.md > README.html
 113 ```
 114
 115 (Using the [Modest style](https://github.com/markdowncss/modest).)