lib: attrs: document functions

lib/attrs.nix

@@ -1,9 +1,21 @@
 { lib, ... }:
 let
-  inherit (lib) filterAttrs mapAttrs';
+  inherit (lib) filterAttrs listToAttrs mapAttrs';
 in
 {
+  # Filter a generated set of attrs using a predicate function.
+  #
+  # mapFilterAttrs ::
+  #   (name -> value -> bool)
+  #   (name -> value -> { name = any; value = any; })
+  #   attrs
   mapFilterAttrs = pred: f: attrs: filterAttrs pred (mapAttrs' f attrs);
 
+  # Generate an attribute set by mapping a function over a list of values.
+  #
+  # genAttrs' ::
+  #   [ values ]
+  #   (value -> { name = any; value = any; })
+  #   attrs
   genAttrs' = values: f: listToAttrs (map f values);
 }