Implement functions

byg/nix/common.nix

@@ -1,7 +1,7 @@
 let
   sources = import ./sources.nix;
   pkgs = import sources.nixpkgs {};
-  haskell = pkgs.haskell.packages.ghc910;
+  haskell = pkgs.haskell.packages.ghc98;
 in
 {
   pkgs = pkgs;