turing machine in nix

1 files changed, 26 insertions, 0 deletions

diff --git a/nix-turing/loop.nix b/nix-turing/loop.nix
new file mode 100644
index 0000000..2849d6a
--- /dev/null
+++ b/nix-turing/loop.nix
@@ -0,0 +1,26 @@
+# defeats the recursion checks of nix and will cause it to
+# loop infinitely. well, almost, anyways.
+#
+# annoyingly, nix doesn't have tail recursion, so actually
+# it'll eventually terminate with a stack overflow.
+let
+  pkgs = import <nixpkgs> {};
+  writeTextVerbose = file: content: pkgs.stdenv.mkDerivation {
+    name = file;
+    src = pkgs.hello;
+    buildPhase = ''
+      echo ${pkgs.lib.escapeShellArg content} > $out
+    '';
+    installPhase = ''
+      echo wrote file to $name
+    '';
+  };
+  storefile = v: writeTextVerbose "nixfile" ''
+    {
+      x = ${toString v};
+    }
+  '';
+  loop = a:
+    let file = import (storefile a);
+    in if file.x == 1 then loop a else "done";
+in loop 1