add hashing.hs

hashing.hs

@@ -0,0 +1,21 @@
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE DerivingStrategies #-}
+
+import Data.Hashable (Hashable (hash))
+import Data.Word (Word8)
+import GHC.Generics (Generic)
+
+data Color =
+    Color
+        { red   :: Word8
+        , green :: Word8
+        , blue  :: Word8
+        }
+    deriving stock (Show, Generic)
+    deriving anyclass (Hashable)
+
+main =
+  do
+    putStrLn (show (hash (Color 255 0 0)))
+    putStrLn (show (hash (Color 0 255 0)))

outputs/hashing.txt

@@ -0,0 +1,2 @@
+7246417153327675019
+7199408575939581793

tools/default.nix

@@ -6,13 +6,10 @@ rec {
 
   inherit (pkgs) callPackage haskellPackages;
 
-  ghc = haskellPackages.ghcWithPackages (p: [
-    p.bytestring
-    p.text
-  ]);
+  haskell = callPackage ./haskell.nix {};
 
   inherit (haskellPackages) ghcid;
 
-  outputs = callPackage ./outputs.nix { inherit ghc; };
+  outputs = callPackage ./outputs.nix { inherit haskell; };
 
 }

tools/haskell.nix

@@ -0,0 +1,7 @@
+{ haskellPackages }:
+
+haskellPackages.ghcWithPackages (p: [
+  p.bytestring
+  p.hashable
+  p.text
+])

tools/outputs.nix

@@ -1,12 +1,12 @@
-{ runCommand, linkFarm, ghc }:
+{ runCommand, linkFarm, haskell }:
 
 let
   run = name: hsFile:
     {
       inherit name;
       path = runCommand "phrasebook-output-${name}.txt"
         {
-          buildInputs = [ ghc ];
+          buildInputs = [ haskell ];
           inherit hsFile;
         }
         ''
@@ -20,4 +20,5 @@ in
     (run "hello-world.txt" ../hello-world.hs)
     (run "common-types.txt" ../common-types.hs)
     (run "variables.txt" ../variables.hs)
+    (run "hashing.txt" ../hashing.hs)
   ]