From 1fea5866aea0aeed2c22dcee20e3fd3f088de3a5 Mon Sep 17 00:00:00 2001
From: "Ricardo M. Correia" <rcorreia@wizy.org>
Date: Wed, 12 Nov 2014 21:36:26 +0100
Subject: [PATCH] Add `unique` list function

It removes duplicate elements from a list.
---
 lib/lists.nix | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/lists.nix b/lib/lists.nix
index 566ee89c95bc..d57c4893daa8 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -223,4 +223,14 @@ rec {
 
   crossLists = f: foldl (fs: args: concatMap (f: map f args) fs) [f];
 
+  # Remove duplicate elements from the list
+  unique = list:
+    if list == [] then
+      []
+    else
+      let
+        x = head list;
+        xs = unique (drop 1 list);
+      in [x] ++ remove x xs;
+
 }