Extract library from `qd`-project

All commits before this point are extracted from the `qd` repository.

The commits have been filtered to only include relevant files. I hope
this is a good compromise between squashing all history and having the
full history of another project attached to this repository.

.gitignore

+*~
+dist-newstyle
+result*

README.md

+# quasar

default.nix

+{ pkgs ? import <nixpkgs> {}, haskellPackages ? pkgs.haskellPackages, args ? {} }:
+
+let
+  drv = haskellPackages.callCabal2nix "quasar" ./. args;
+
+in
+  if pkgs.lib.inNixShell then drv.env else drv

flake.lock

+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1623154001,
+        "narHash": "sha256-KxsIXg5ez5SveGayOKcW+MnofqVuLnwZHE5mZgtRAJo=",
+        "path": "/nix/store/r35z76cadipjzjrjik06gp1kfbqlhdck-source",
+        "rev": "3bc8e5cd23b84b2e149e7aaad57117da16a19e6f",
+        "type": "path"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

+{
+  outputs = { self, nixpkgs }:
+  with nixpkgs.lib;
+  let
+    forAllSystems = genAttrs ["x86_64-linux" "aarch64-linux"];
+    pkgs = forAllSystems (system: import nixpkgs { inherit system; overlays = [ self.overlay ]; });
+  in {
+
+    devShell = forAllSystems (system: pkgs.${system}.haskellPackages.quasar.env);
+
+    defaultPackage = forAllSystems (system: pkgs.${system}.haskellPackages.quasar);
+
+    overlay = final: prev: {
+      haskell = prev.haskell // {
+        packageOverrides = hfinal: hprev: prev.haskell.packageOverrides hfinal hprev // {
+          quasar = import ./. {
+            pkgs = final;
+            haskellPackages = hfinal;
+          };
+        };
+      };
+    };
+
+  };
+}

quasar.cabal

+cabal-version: 3.0
+
+name:           quasar
+version:        0.1.0.0
+license:        NONE
+build-type:     Simple
+extra-source-files:
+    README.md
+
+--source-repository head
+--  type: git
+--  location: https://git.c3pb.de/jens/quasar.git
+
+common shared-properties
+  default-extensions:
+    AllowAmbiguousTypes
+    BangPatterns
+    DataKinds
+    DefaultSignatures
+    DeriveAnyClass
+    DeriveGeneric
+    DerivingStrategies
+    DuplicateRecordFields
+    ExistentialQuantification
+    FlexibleContexts
+    FlexibleInstances
+    FunctionalDependencies
+    GADTs
+    GeneralizedNewtypeDeriving
+    InstanceSigs
+    LambdaCase
+    MultiParamTypeClasses
+    NamedFieldPuns
+    NoImplicitPrelude
+    OverloadedStrings
+    RankNTypes
+    ScopedTypeVariables
+    StandaloneDeriving
+    TemplateHaskell
+    TupleSections
+    TypeApplications
+    TypeFamilies
+    TypeOperators
+  build-depends:
+    base >=4.7 && <5,
+    binary,
+    ghc-prim,
+    hashable,
+    microlens-platform,
+    mtl,
+    template-haskell,
+    transformers,
+    unordered-containers,
+  default-language: Haskell2010
+  ghc-options: -fwarn-unused-do-bind -fwarn-tabs -Wall -Wincomplete-uni-patterns -Wpartial-fields
+
+common shared-executable-properties
+  import: shared-properties
+  ghc-options: -fwarn-unused-do-bind -fwarn-tabs -Wall -Wincomplete-uni-patterns -Wpartial-fields -threaded -rtsopts "-with-rtsopts=-N -I0"
+
+library
+  import: shared-properties
+  exposed-modules:
+  hs-source-dirs:
+    src
+
+test-suite quasar-test
+  import: shared-executable-properties
+  type: exitcode-stdio-1.0
+  build-depends:
+    quasar,
+    hspec,
+  main-is: Spec.hs
+  other-modules:
+  hs-source-dirs:
+    test