Simplify nix source code

ns3-simulations/nix/default.nix

@@ -1,5 +1,58 @@
-with (import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/19.03.tar.gz") {});
-rec {
-   ns3 = callPackage ./ns3 { inherit stdenv; inherit fetchurl; inherit python; inherit gsl; };
-   simulator = callPackage ./simulator { inherit stdenv; inherit ns3; };
+{
+  pkgs ? (import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/19.03.tar.gz") {})
+}:
+
+with pkgs; rec {
+
+     ns3 = stdenv.mkDerivation rec {
+        ##### Configure NIX #####
+        name="ns3";
+        sourceRoot="ns-allinone-3.29/ns-3.29/"; # Since we have 2 source tarball (ns-3 & ECOFEN) nix need to know which one to use
+
+        ##### Fetch ns-3 And ECOFEN #####
+        src = [
+            (fetchurl {
+            url = https://www.nsnam.org/releases/ns-allinone-3.29.tar.bz2;
+            sha256 = "0m9dpmby116qk1m4x645i1p92syn30yzn9dgxxji5i25g30abpsd";
+            })
+
+            (fetchurl {
+            url = http://people.irisa.fr/Anne-Cecile.Orgerie/ECOFEN/ecofen-v2.tar.bz2;
+            sha256 = "1dnmm20ihas6hwwb8qbx8sr3h66nrg8h55x6f2aqpf3xima29dyh";
+            })
+        ];
+
+        ##### Configure Dependencies #####
+        buildInputs= [ python gsl ];
+
+        ##### Configure Phases #####
+        postUnpack=''mv ecofen-module-v2 ${sourceRoot}/contrib/ecofen'';
+        configurePhase=''
+        export CXXFLAGS="-Wall -g -O0" # Don't treat warning as error when compiling ns-3
+        python2 waf configure
+        '';
+        buildPhase=''python2 waf'';
+        installPhase=''
+        mkdir -p $out/include
+        cp -r ./build/lib $out/
+        cp -r ./build/ns3 $out/include
+        '';
+    };
+    
+    simulator= stdenv.mkDerivation rec {
+        ##### Configure NIX #####
+        name="simulator";
+        src=./simulator;
+
+        #####  Export ns3 location #####
+        NS3_PATH=ns3;
+
+        ##### Configure Phases #####
+        buildPhase=''make'';
+        installPhase=''
+        mkdir -p $out/bin
+        install -D -t $out/bin simulator
+        '';
+
+      };
 }

ns3-simulations/nix/ns3/default.nix

@@ -1,36 +0,0 @@
-{ stdenv, fetchurl, python, gsl }:
-
-stdenv.mkDerivation rec {
-  ##### Configure NIX #####
-  name="ns3";
-  sourceRoot="ns-allinone-3.29/ns-3.29/"; # Since we have 2 source tarball (ns-3 & ECOFEN) nix need to know which one to use
-
-  ##### Fetch ns-3 And ECOFEN #####
-  src = [
-      (fetchurl {
-      url = https://www.nsnam.org/releases/ns-allinone-3.29.tar.bz2;
-      sha256 = "0m9dpmby116qk1m4x645i1p92syn30yzn9dgxxji5i25g30abpsd";
-      })
-      
-      (fetchurl {
-      url = http://people.irisa.fr/Anne-Cecile.Orgerie/ECOFEN/ecofen-v2.tar.bz2;
-      sha256 = "1dnmm20ihas6hwwb8qbx8sr3h66nrg8h55x6f2aqpf3xima29dyh";
-      })
-  ];
-
-  ##### Configure Dependencies #####
-  buildInputs= [ python gsl ];
-
-  ##### Configure Phases #####
-  postUnpack=''mv ecofen-module-v2 ${sourceRoot}/contrib/ecofen'';
-  configurePhase=''
-  export CXXFLAGS="-Wall -g -O0" # Don't treat warning as error when compiling ns-3
-  python2 waf configure
-  '';
-  buildPhase=''python2 waf'';
-  installPhase=''
-  mkdir -p $out/include
-  cp -r ./build/lib $out/
-  cp -r ./build/ns3 $out/include
-  '';
-}

ns3-simulations/nix/simulator/default.nix

@@ -1,18 +0,0 @@
-{ stdenv, ns3 }:
-
-stdenv.mkDerivation rec {
-  ##### Configure NIX #####
-  name="simulator";
-  src=./src;
-
-  #####  Export ns3 location #####
-  NS3_PATH=ns3;
-
-  ##### Configure Phases #####
-  buildPhase=''make'';
-  installPhase=''
-  mkdir -p $out/bin
-  install -D -t $out/bin simulator
-  '';
-
-}