diff --git a/.gitignore b/.gitignore
index 3a0388c..81a689c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ kalk/Cargo.lock
 cli/Cargo.lock
 cli/test
 .vscode/
+result*
diff --git a/Cargo.lock b/Cargo.lock
index 49401c9..603173c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -152,9 +152,8 @@ dependencies = [
 
 [[package]]
 name = "gmp-mpfr-sys"
-version = "1.4.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a57fdb339d49833021b1fded600ed240ae907e33909d5511a61dff884df7f16e"
+version = "1.4.7"
+source = "git+https://gitlab.com/tspiteri/gmp-mpfr-sys.git#21966f4bfb56c87d407eb14c72e92ef4e55856aa"
 dependencies = [
  "libc",
  "winapi",
diff --git a/Cargo.toml b/Cargo.toml
index ed4a5eb..3b2e286 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,3 +1,6 @@
+[patch.crates-io]
+gmp-mpfr-sys = { git = "https://gitlab.com/tspiteri/gmp-mpfr-sys.git" }
+
 [workspace]
 members = ["kalk", "cli"]
 
diff --git a/README.md b/README.md
index 382882a..0ce4ec6 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ Kalker (or "kalk") is a calculator program/website that supports user-defined va
 
 * Operators: `+`, `-`, `*`, `/`, `!`
 * Groups: `()`, `⌈ceil⌉`, `⌊floor⌋`, `[iverson]`
-* [Pre-defined functions and constants](https://github.com/PaddiM8/kalker/blob/master/kalk/src/prelude.rs)
+* [Pre-defined functions and constants](https://github.com/PaddiM8/kalker/blob/master/kalk/src/prelude/mod.rs)
 * User-defined functions and variables. `f(x, y) = xy`, `x = 5`
 * Derivative of functions (derivatives of noisy functions or of higher order can be a bit inaccurate). `f'(2)`, `sin'(-pi)`
 * Integration. `∫(0, pi, sin(x) dx)` or `∫(0, π, sin(x) dx)`, maybe sometimes be slightly off
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..4fb93ff
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1632255010,
+        "narHash": "sha256-p/BYR6qhbCtDpOfw9uMYwjwyhuCVKgiSUpKZaV/63UE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "bfc38d3d0d22c528e8abc46c5dd5f3f50fc4554b",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..7f175ed
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,58 @@
+{
+  description = "A calculator program/website";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems =
+        [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+
+      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
+
+      nixpkgsFor = forAllSystems (system:
+        import nixpkgs {
+          inherit system;
+          overlays = [ self.overlay ];
+        });
+    in {
+      overlay = final: prev: {
+        kalker = final.rustPlatform.buildRustPackage {
+          pname = "kalker";
+          version = "unstable";
+
+          src = self;
+
+          outputs = [ "out" "lib" ];
+
+          postInstall = ''
+            moveToOutput "lib" "$lib"
+          '';
+
+          cargoLock = {
+            lockFile = self + "/Cargo.lock";
+            outputHashes = {
+              "gmp-mpfr-sys-1.4.7" =
+                "sha256-zHpGbEgh3MgAUVdlWrXq4Clj1boybi6DMOcsjgZbAh0=";
+            };
+          };
+
+          buildInputs = with final; [ gmp mpfr libmpc ];
+
+          CARGO_FEATURE_USE_SYSTEM_LIBS = "1";
+        };
+      };
+
+      packages =
+        forAllSystems (system: { inherit (nixpkgsFor.${system}) kalker; });
+
+      defaultPackage = forAllSystems (system: self.packages.${system}.kalker);
+
+      apps = forAllSystems (system: {
+        kalker = {
+          type = "app";
+          program = "${self.packages.${system}.kalker}/bin/kalker";
+        };
+      });
+
+      defaultApp = forAllSystems (system: self.apps.${system}.kalker);
+    };
+}