An @-sign in a box, in haskell

Initial commit of a Haskell version of Xanthous, written using Brick and
built with Nix.

This is so much nicer and so much easier

shell.nix

@@ -0,0 +1,28 @@
+{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc865", withHoogle ? true }:
+let
+  inherit (nixpkgs) pkgs;
+
+  xan = import ./xanthous.nix;
+
+  packageSet = (
+    if compiler == "default"
+    then pkgs.haskellPackages
+    else pkgs.haskell.packages.${compiler}
+  );
+
+  haskellPackages = (
+    if withHoogle
+    then packageSet.override {
+      overrides = (self: super: {
+        ghc = super.ghc // { withPackages = super.ghc.withHoogle; };
+        ghcWithPackages = self.ghc.withPackages;
+      });
+    }
+    else packageSet
+  );
+
+  drv = haskellPackages.callPackage xan {};
+
+  inherit (pkgs.haskell.lib) addBuildTools;
+in
+(addBuildTools drv (with haskellPackages; [ cabal-install ])).env