add some support functions

functions/flatten.nix

@@ -0,0 +1,11 @@
+with builtins;
+let flatten-once = foldl' (x: y: x ++ (if isList y then y else [y])) []; # curried.  takes a list as final arg.
+    flatten-many' = flatten-many': l:
+      let flattened = flatten-once l;
+      in
+        if flattened == l
+	  then l
+	  else flatten-many' flatten-many' flattened;
+    flatten-many = flatten-many' flatten-many';
+in
+flatten-many

functions/join-string.nix

@@ -0,0 +1,12 @@
+with builtins;
+
+let join' = join': sep: sl:
+      if sl == []
+        then ""
+        else if length sl == 1
+          then head sl
+	  else "${head sl}${sep}${join' join' sep (tail sl)}";
+    join = join' join';
+in
+
+join

functions/match-all-flat.nix

@@ -0,0 +1,3 @@
+with import (toString ./.);
+
+with builtins; pattern: s: flatten (match-all pattern s)

functions/match-all.nix

@@ -0,0 +1 @@
+with builtins; pattern: s: filter isList (split pattern s)

functions/name-to-mac.nix

@@ -0,0 +1,4 @@
+with import (toString ./.);
+with builtins;
+
+elts: name: join-string ":" (take elts (match-all-flat "(..)" (hashString "sha256" name)))

functions/take.nix

@@ -0,0 +1,11 @@
+with builtins;
+
+let take' = take': n: l: 
+      if n < 0 then throw "take requires a positive whole number or 0." else
+      if n == 0 || l == []
+        then []
+	else [ (head l) ] ++ (take' take' (n - 1) (tail l));
+    take = take' take';
+in
+
+take