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 Install Ghcup following [the instructions](https://www.haskell.org/ghcup/install/#installation), making sure to load the updated environment with
  16
  17 ```bash
  18 source /home/neil/.ghcup/env
  19 ```
  20
  21 and then set the default GHC to use with `ghcup set ghc 9.0.1` .
  22
  23 Install [Haskell Language Server](https://haskell-language-server.readthedocs.io/en/latest/configuration.html) for Sublime Text
  24
  25
  26 ## Creating the repository and project
  27 Create the repository as normal: create the project in Gitolite, clone it, and insert the `.gitignore` and `README.md` files.
  28
  29 There's one package per day, with the code for each package in sub-directories of the root directory.
  30
  31 Create the basic `cabal` project.
  32
  33 ```
  34 cabal init
  35 ```
  36
  37 Modify the `advent-of-code21.cabal` file as needed, such as updating the Cabal version and writing the `common` stanzas.
  38
  39 ## Creating subsequent days
  40
  41 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).)
  42
  43 Compile with
  44 ```
  45 cabal build
  46 ```
  47 or
  48 ```
  49 cabal build advent01
  50 ```
  51
  52 Run with
  53 ```
  54 cabal run advent01
  55 ```
  56
  57 If you want to pass in additional RTS parameters, do it like this:
  58 ```
  59 stack exec -- advent01 +RTS -K0 -RTS
  60 ```
  61
  62 Run interactively with
  63 ```
  64 cabal repl advent01
  65 ```
  66 or
  67 ```
  68 stack ghci advent01:exe:advent01
  69 ```
  70 if the first form is ambiguous.
  71
  72 To profile, use
  73 ```
  74 stack build --executable-profiling --library-profiling --ghc-options="-fprof-auto -rtsopts" advent01
  75 ```
  76 then run with
  77 ```
  78 stack exec --profile -- advent01 +RTS -p -hy
  79 ```
  80 Generate the profile graph with
  81 ```
  82 stack exec hp2ps advent01.hp
  83 ```
  84
  85 For Cabal, look at [profiling with Cabal sandboxes](https://nikita-volkov.github.io/profiling-cabal-projects/)
  86
  87
  88 # Packages
  89
  90 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).
  91
  92 Packages I used a lot:
  93
  94 * [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.
  95 * [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).
  96
  97 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).
  98
  99 Packages I didn't use much, but need to remember:
 100
 101 * [Arithmoi](https://hackage.haskell.org/package/arithmoi) for number theory
 102 * [Pointed List](https://hackage.haskell.org/package/pointedlist-0.6.1) for zipper lists (sometimes circular)
 103 * [Vector](https://hackage.haskell.org/package/vector) for array-like things
 104 * [Linear](https://hackage.haskell.org/package/linear) for coordinate-vector like things
 105 * [Grid](https://hackage.haskell.org/package/grid) for 2-d grids
 106 * [Graph-wrapper](https://hackage.haskell.org/package/graph-wrapper) for graphs
 107 * [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.
 108 * [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
 109 * [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/)
 110 * [Replace-Megaparsec](https://github.com/jamesdbrock/replace-megaparsec), for using Mpc for all sorts of things traditionally done with regex substitutions.
 111
 112 # Readme
 113
 114 Build this readme file wth
 115 ```
 116 pandoc -s README.md > README.html
 117 ```
 118
 119 (Using the [Modest style](https://github.com/markdowncss/modest).)