Add nix flake to allow for easy setup and reproducable builds

.gitignore

@@ -41,3 +41,6 @@ _start-cmd.bat
 
 # Wiki
 wiki
+
+# nix output
+result

flake.nix

@@ -0,0 +1,91 @@
+{
+  description = "Generator for Geometric Inhomogeneous Random Graphs";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+      in
+      {
+        packages.default = pkgs.stdenv.mkDerivation {
+          pname = "girgs";
+          version = "1.0.2";
+
+          src = ./.;
+
+          nativeBuildInputs = with pkgs; [
+            cmake
+            ninja
+          ];
+
+          buildInputs = with pkgs; [
+            boost
+            gtest
+            doxygen
+            graphviz
+          ];
+
+          cmakeFlags = [
+            "-DCMAKE_BUILD_TYPE=Release"
+            "-DOPTION_BUILD_TESTS=ON"
+            "-DOPTION_BUILD_EXAMPLES=ON"
+            "-DOPTION_BUILD_CLI=ON"
+          ];
+
+          meta = with pkgs.lib; {
+            description = "Generator for Geometric Inhomogeneous Random Graphs";
+            homepage = "https://github.com/chistopher/girgs";
+            license = {
+              fullName = "MIT License";
+              url = "https://opensource.org/licenses/MIT";
+              spdxId = "MIT";
+              file = ./LICENSE;
+            };
+            platforms = platforms.unix;
+            maintainers = with maintainers; [ 
+              (maintainers.lib.maintainer {
+                name = "Dennis Kobert";
+                email = "dennis@kobert.dev";
+                github = "TrueDoctor";
+              })
+            ];
+          };
+        };
+
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            cmake
+            ninja
+            boost
+            gtest
+            doxygen
+            graphviz
+            gcc
+            gdb
+            valgrind
+            ccache
+            clang-tools # For clang-format, clang-tidy
+            pre-commit
+          ];
+
+          # Set environment variables for development
+          shellHook = ''
+            echo "Welcome to GIRGS development environment!"
+            echo "Build tools and dependencies are available."
+
+            # Setup ccache
+            export CCACHE_DIR=$PWD/.ccache
+            export PATH="${pkgs.ccache}/bin:$PATH"
+
+            # Make tests verbose by default
+            export CTEST_OUTPUT_ON_FAILURE=1
+          '';
+        };
+      }
+    );
+}