1 files changed, 17 insertions, 2 deletions
diff --git a/src/compiler/GF/Data/Utilities.hs b/src/compiler/GF/Data/Utilities.hs
index eac315508..29ed329dc 100644
--- a/src/compiler/GF/Data/Utilities.hs
+++ b/src/compiler/GF/Data/Utilities.hs
@@ -12,12 +12,12 @@
 -----------------------------------------------------------------------------
 
 
-module GF.Data.Utilities(module GF.Data.Utilities, module PGF.Utilities) where
+module GF.Data.Utilities(module GF.Data.Utilities) where
 
 import Data.Maybe
 import Data.List
 import Control.Monad (MonadPlus(..),liftM,when)
-import PGF.Utilities
+import qualified Data.Set as Set
 
 -- * functions on lists
 
@@ -190,3 +190,18 @@ joinS glue = concatS . intersperse (showString glue)
 
 
 
+-- | Like 'Data.List.nub', but O(n log n) instead of O(n^2), since it uses a set to lookup previous things.
+--   The result list is stable (the elements are returned in the order they occur), and lazy.
+--   Requires that the list elements can be compared by Ord.
+--   Code ruthlessly taken from <http://hpaste.org/54411>
+nub' :: Ord a => [a] -> [a]
+nub' = loop Set.empty
+    where loop _    []            = []
+          loop seen (x : xs)
+              | Set.member x seen = loop seen xs
+              | otherwise         = x : loop (Set.insert x seen) xs
+
+
+-- | Replace all occurences of an element by another element.
+replace :: Eq a => a -> a -> [a] -> [a]
+replace x y = map (\z -> if z == x then y else z)