ToyLib

ToyLib is my Haskell library for solving AtCoder problems. Note that most of the contents has been ported into the Extra module of ac-library-hs.

API documentation

CLI

toy-lib-exe is the source file bunlder.

Usage

Generate a template that bundles all the source files:

$ cabal run toy-lib-exe > template.hs

Minify the toy-lib modules and their dependencies into one line:

$ cabal run toy-lib-exe -m Data.Graph.Sparse Data.UnionFind.Mutable

Embed toy-lib modules:

$ cat Example.hs
-- {{{ toy-lib import
import Math.Manhattan
-- }}} toy-lib import

$ cabal run toy-lib-exe -e Examle.hs
rot45 :: (Int, Int) -> (Int, Int);rot45 (!x, !y) = (x - y, x + y)

Project setting notes

Installation

As of 2025, AtCoder is using GHC 9.8.4 (Source: 使用できる言語とライブラリの一覧). Install GHC 9.8.4 and the corresponding tools with ghcup.

If you're a Nix Flakes user, run direnv allow to enable nix-direnv.

toy-lib.cabal

No explicit exports are assumed, as they're bundled into one file (Main.hs):

ghc-options:
- -Wno-missing-export-lists

We're using Haskell2010 because haskell-src-exts (the parser) does not understand GHC2021, but all the extensions enabled by GHC20210 are enabled via default-extensisons:

default-language: Haskell2010

default-extensions:
- BangPatterns
# and lots more

Limitations

We have limitations coming from haskell-src-exts:

• Can't use MultiWayIf
haskell-src-exts does not understand it well.

• Can't use GHC2021 syntax
  For example import X qualified as Y is not available.

Useful commands

See the Justfile for details. Otherwise, you could run the following commands manually.

doctest

Run doctest via REPL:

$ cabal repl --with-ghc=doctest --repl-options='-w -Wdefault'

haddock

Run haddock from command line:

$ cabal haddock
$ cabal haddock --open

Similar repositories

• cojna/iota iota is surely the best resource!
• meooow25/haccepted Beautiful library compatible with Codeforces.
• minoki/my-atcoder-solutions Solutions to EDPC and more.
• unnohideyuki/AtHaskell
• mizunashi-mana/haskell-atcoder-template