Compatibility with base 4.11

4d-labyrinth.cabal

@@ -17,7 +17,7 @@ cabal-version:       >=1.10
 executable 4d-labyrinth
   main-is:             Main.hs
   other-modules:       Object
-                       Objects.Cube, Objects.Octahedron
+                       Objects.Cube, Objects.Octahedron, Objects.Diamond
                        Transformation, Scene, SceneTO
                        Wireframe
                        Render
@@ -39,6 +39,6 @@ executable 4d-labyrinth
                        RotationMethods
   other-extensions:    TemplateHaskell, Rank2Types, ScopedTypeVariables
                        DeriveFunctor
-  build-depends:       base >=4.9 && <4.11, OpenGL >=3.0 && <3.1, MonadRandom >=0.5 && <0.6, sdl2 >=2.2 && <2.5, lens >=4.15 && <4.17, linear >=1.20 && <1.21, containers >=0.5 && <0.6, bytestring >=0.10 && <0.11, filepath >=1.4 && <1.5, adjunctions >=4.3 && <4.5, array >=0.5 && <0.6, mtl >=2.2 && <2.3
+  build-depends:       base >=4.9 && <4.12, OpenGL >=3.0 && <3.1, MonadRandom >=0.5 && <0.6, sdl2 >=2.2 && <2.5, lens >=4.15 && <4.17, linear >=1.20 && <1.21, containers >=0.5 && <0.6, bytestring >=0.10 && <0.11, filepath >=1.4 && <1.5, adjunctions >=4.3 && <4.5, array >=0.5 && <0.6, mtl >=2.2 && <2.3
   hs-source-dirs:      src
   default-language:    Haskell2010

shell.nix

@@ -0,0 +1,34 @@
+{ nixpkgs ? import <nixpkgs> {}, compiler ? "default", doBenchmark ? false }:
+
+let
+
+  inherit (nixpkgs) pkgs;
+
+  f = { mkDerivation, adjunctions, array, base, bytestring
+      , containers, filepath, lens, linear, MonadRandom, mtl, OpenGL
+      , sdl2, stdenv
+      }:
+      mkDerivation {
+        pname = "4d-labyrinth";
+        version = "0.1.0.0";
+        src = ./.;
+        isLibrary = false;
+        isExecutable = true;
+        executableHaskellDepends = [
+          adjunctions array base bytestring containers filepath lens linear
+          MonadRandom mtl OpenGL sdl2
+        ];
+        license = stdenv.lib.licenses.gpl3;
+      };
+
+  haskellPackages = if compiler == "default"
+                       then pkgs.haskellPackages
+                       else pkgs.haskell.packages.${compiler};
+
+  variant = if doBenchmark then pkgs.haskell.lib.doBenchmark else pkgs.lib.id;
+
+  drv = variant (haskellPackages.callPackage f {});
+
+in
+
+  if pkgs.lib.inNixShell then drv.env else drv

src/Transformation.hs

@@ -76,11 +76,14 @@ rotation plane angle = Transformation
     l = column plane . plane
 
 -- Composition and identity transformation.
+instance (SomeVector v, Num a) =>
+  Semigroup (Transformation v a) where
+  Transformation rot2 trans2 <> Transformation rot1 trans1 =
+    Transformation (rot2 !*! rot1) ((rot2 !* trans1) ^+^ trans2)
+
 instance (SomeVector v, Num a) =>
   Monoid (Transformation v a) where
   mempty = Transformation identity zero
-  mappend (Transformation rot2 trans2) (Transformation rot1 trans1) =
-    Transformation (rot2 !*! rot1) ((rot2 !* trans1) ^+^ trans2)
 
 -- Actually, rigid transformations form a group, not just a monoid.
 -- (And computing the inverse is not very expensive,