diff --git a/pkgs/development/libraries/haskell/cabal/cabal.nix b/pkgs/development/libraries/haskell/cabal/cabal.nix
index 154463e04dc..1e08a819c0e 100644
--- a/pkgs/development/libraries/haskell/cabal/cabal.nix
+++ b/pkgs/development/libraries/haskell/cabal/cabal.nix
@@ -27,9 +27,10 @@ attrs :
             };
 
             # default buildInputs are just ghc, if more buildInputs are required
-            # buildInputs can be extended by the client, but often propagatedBuildInputs
-            # is preferable anyway
-            buildInputs = [attrs.ghc];
+            # buildInputs can be extended by the client by using extraBuildInputs,
+            # but often propagatedBuildInputs is preferable anyway
+            buildInputs = [attrs.ghc] ++ self.extraBuildInputs;
+            extraBuildInputs = [];
 
             # we make sure that propagatedBuildInputs is defined, so that we don't
             # have to check for its existence
@@ -79,11 +80,13 @@ attrs :
               ./Setup copy
               ./Setup register --gen-script
               mkdir -p $out/nix-support
-              sed -i 's/|.*\(ghc-pkg update\)/| \1/' register.sh
-              cp register.sh $out/nix-support/register-ghclib.sh
-              sed -i 's/\(ghc-pkg update\)/\1 --user/' register.sh
-              mkdir -p $out/bin
-              cp register.sh $out/bin/register-${self.name}.sh
+              if test -f register.sh; then
+                sed -i 's/|.*\(ghc-pkg update\)/| \1/' register.sh
+                cp register.sh $out/nix-support/register-ghclib.sh
+                sed -i 's/\(ghc-pkg update\)/\1 --user/' register.sh
+                mkdir -p $out/bin
+                cp register.sh $out/bin/register-${self.name}.sh
+              fi
 
               eval "$postInstall"
             '';
diff --git a/pkgs/development/tools/documentation/haddock/default.nix b/pkgs/development/tools/documentation/haddock/default.nix
index a38db0977d6..86d07b240a5 100644
--- a/pkgs/development/tools/documentation/haddock/default.nix
+++ b/pkgs/development/tools/documentation/haddock/default.nix
@@ -1,25 +1,11 @@
-{stdenv, fetchurl, ghc}:
+{cabal}:
 
-stdenv.mkDerivation (rec {
+cabal.mkDerivation (self : {
   pname = "haddock";
   version = "2.0.0.0";
-  name = "${pname}-${version}";
-  src = fetchurl {
-    url = "http://hackage.haskell.org/packages/archive/${pname}/${version}/${name}.tar.gz";
-    sha256 = "a2ea5bdc127bc8b189a8d869f582ec774fea0933e7f5ca89549a6c142b9993df";
+  name = self.fname;
+  sha256 = "a2ea5bdc127bc8b189a8d869f582ec774fea0933e7f5ca89549a6c142b9993df";
+  meta = {
+    description = "a tool for automatically generating documentation from annotated Haskell source code";
   };
-  buildInputs = [ghc];
-
-  configurePhase = '' 
-    ghc --make Setup.lhs
-    ./Setup configure -v --prefix="$out"
-  '';
-
-  buildPhase = ''
-    ./Setup build
-  '';
-
-  installPhase = ''
-    ./Setup install
-  '';
 })
diff --git a/pkgs/development/tools/parsing/happy/happy-1.17.nix b/pkgs/development/tools/parsing/happy/happy-1.17.nix
index 663dc15bc51..b7fa22ccb80 100644
--- a/pkgs/development/tools/parsing/happy/happy-1.17.nix
+++ b/pkgs/development/tools/parsing/happy/happy-1.17.nix
@@ -1,28 +1,12 @@
-{stdenv, fetchurl, perl, ghc}:
+{cabal, perl}:
 
-stdenv.mkDerivation (rec {
+cabal.mkDerivation (self : {
 
   # requires cabal-1.2 (and therefore, in Nix, currently ghc-6.8)
 
   pname = "happy";
   version = "1.17";
-  name = "${pname}-${version}";
-  src = fetchurl {
-    url = "http://www.haskell.org/happy/dist/${version}/${name}.tar.gz";
-    sha256 = "dca4e47d17e5d538335496236b3d2c3cbff644cf7380c987a4714e7784c70a2b";
-  };
-  buildInputs = [ghc perl];
-
-  configurePhase = "
-    ghc --make Setup.lhs
-    ./Setup configure --prefix=\"\${out}\"
-  ";
-
-  buildPhase = "
-    ./Setup build
-  ";
-
-  installPhase = "
-    ./Setup install
-  ";
+  name = self.fname;
+  sha256 = "dca4e47d17e5d538335496236b3d2c3cbff644cf7380c987a4714e7784c70a2b";
+  extraBuildInputs = [perl];
 })
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 5a4a849df42..1b201910863 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1498,8 +1498,7 @@ rec {
   };
 
   haddock = import ../development/tools/documentation/haddock {
-    inherit fetchurl stdenv;
-    ghc = ghc68;
+    cabal = cabal68;
   };
 
   happy = import ../development/tools/parsing/happy {
@@ -1507,8 +1506,8 @@ rec {
   };
 
   happy117 = import ../development/tools/parsing/happy/happy-1.17.nix {
-    inherit fetchurl stdenv perl;
-    ghc = ghc68;  # because happy-1.17 depends on cabal-1.2
+    inherit perl;
+    cabal = cabal68;  # because happy-1.17 depends on cabal-1.2
   };
 
   help2man = import ../development/tools/misc/help2man {