adds forAllSupported

default.nix

@@ -0,0 +1,26 @@
+rec {
+  # copied from <nixpkgs/lib>
+  genAttrs = names: f:
+    builtins.listToAttrs (map (n: { name = n; value = f n; }) names);
+
+  # The list of systems supported by nixpkgs and hydra
+  supportedSystems = [
+    "aarch64-linux"
+    "i686-linux"
+    "x86_64-darwin"
+    "x86_64-linux"
+  ];
+
+  # Returns an attribute set with all the supported systems as keys and the
+  # output of the passed function with each system passed to it.
+  #
+  # This is useful in the flake outputs because the outputs return static sets
+  # that map to the different systems.
+  #
+  # Example:
+  #   forAllSupported (x: null)
+  #   > { aarch64-linux = null; i686-linux = null; x86_64-darwin = null;
+  #   > x86_64-linux = null; }
+  # (system -> attrs) -> attrs
+  forAllSupported = genAttrs supportedSystems;
+}

flake.nix

@@ -0,0 +1,7 @@
+{
+  description = "Pure Nix flake utility functions";
+  edition = 201909;
+  outputs = { self }: {
+    lib = import ./.;
+  };
+}