feat: add Adlude module

README.md

@@ -7,23 +7,10 @@
 This project is usable either via `nix` or via `cabal`. I will provide
 commands for both in the following sections.
 
-### run all solutions
 
-#### nix
-
-```sh
-nix run .#aoc
-```
-
-#### cabal
-
-```sh
-cabal run exe:aoc
-```
-
-### run specific solution
+### running solution
 
-It is possible to run only a specific day. In this example day # `01` is ran.
+In this example day # `01` is ran.
 
 #### nix
 

aoc.cabal

@@ -74,17 +74,9 @@ library lib
     , text
 
   hs-source-dirs:  lib
-  exposed-modules: Parsing
-
-executable aoc
-  import:         shared
-  build-depends:
-    , base
-    , containers
-    , text
-
-  hs-source-dirs: .
-  main-is:        Main.hs
+  exposed-modules:
+    Adlude
+    Parsing
 
 executable 01
   import:         shared

flake.nix

@@ -48,8 +48,8 @@
           };
         };
 
-        packages.default = self'.packages.aoc;
-        apps.default = self'.apps.aoc;
+        packages.default = self'.packages."01";
+        apps.default = self'.apps."01";
 
         devShells.default = pkgs.mkShell {
           name = "aoc";

lib/Adlude.hs

@@ -0,0 +1,30 @@
+-- | `Prelude` for Advent of Code problems.
+module Adlude (
+  pickOne,
+  countBy,
+  count,
+  counts,
+  partialSums,
+) where
+
+import Data.Foldable (toList)
+import Data.List (foldl', inits, scanl', tails)
+import Data.Map (Map)
+import Data.Map qualified as Map
+
+pickOne :: [a] -> [(a, [a])]
+pickOne xs = do
+  (ys, x : zs) <- zip (inits xs) (tails xs)
+  return (x, ys ++ zs)
+
+countBy :: (Foldable f) => (a -> Bool) -> f a -> Int
+countBy p = foldl' (\acc x -> if p x then acc + 1 else acc) 0
+
+count :: (Foldable f, Eq a) => a -> f a -> Int
+count = countBy . (==)
+
+counts :: (Foldable f, Ord a) => f a -> Map a Int
+counts xs = Map.fromListWith (+) [(x, 1) | x <- toList xs]
+
+partialSums :: (Num a) => [a] -> [a]
+partialSums = scanl' (+) 0