Add Nix flake

Author: splintersuidman

flake.lock

@@ -0,0 +1,48 @@
+{
+  description = "Explorations in combinatory logic with Agda";
+
+  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};
+          agdaPackages = pkgs.agdaPackages;
+
+          version = "0";
+          everythingFile = "./index.agda";
+      in {
+        packages.combinatory-logic = agdaPackages.mkDerivation {
+          inherit version;
+          pname = "combinatory-logic";
+          src = ./.;
+          buildInputs = [ agdaPackages.standard-library ];
+          inherit everythingFile;
+        };
+
+        packages.combinatory-logic-doc = agdaPackages.mkDerivation {
+          inherit version;
+          pname = "combinatory-logic-doc";
+          src = ./.;
+          buildInputs = [ agdaPackages.standard-library ];
+
+          buildPhase = ''
+            runHook preBuild
+            agda -i ${dirOf everythingFile} --html ${everythingFile} --html-dir html
+            runHook postBuild
+          '';
+
+          installPhase = ''
+            runHook preInstall
+            mkdir -p $out
+            mkdir -p $out/doc
+            cp html/* $out/doc
+            runHook postInstall
+          '';
+        };
+
+        defaultPackage = self.packages.${system}.combinatory-logic;
+      });
+}