fix travis script

.travis.yml

@@ -1,3 +1,3 @@
 language: haskell
 after_script:
-  - "cat dist/test/operational-transformation-*-tests.log"
+  - "cat dist/test/ot-*-tests.log"

src/Data/Text/Rope.hs

@@ -0,0 +1,61 @@
+{-# LANGUAGE MultiParamTypeClasses, GeneralizedNewtypeDeriving #-}
+
+module Data.Text.Rope
+  ( CharOffset (..)
+  , Rope
+  , empty
+  , null
+  , splitAt
+  , take
+  , drop
+  , concat
+  , isPrefixOf
+  ) where
+
+import Prelude hiding (splitAt, take, drop, null, concat)
+import Data.FingerTree (viewr, ViewR (..), viewl, ViewL (..), Measured (..), (<|), (|>), split)
+import qualified Data.FingerTree as FT
+import qualified Data.Text as T
+import Data.Monoid
+import Data.Foldable (toList)
+
+newtype CharOffset = CharOffset { getCharOffset :: Int } deriving (Enum, Real, Ord, Eq, Num, Integral)
+
+type Rope = FT.FingerTree CharOffset T.Text
+
+instance Monoid CharOffset where
+  mempty = CharOffset 0
+  mappend = (+)
+
+instance Measured CharOffset T.Text where
+  measure = CharOffset . T.length
+
+empty :: Rope
+empty = FT.empty
+
+null :: Rope -> Bool
+null r = case viewl r of
+  EmptyL -> True
+  x :< xs -> T.null x && null xs
+
+splitAt :: CharOffset -> Rope -> (Rope, Rope)
+splitAt n r = case viewr lr of
+    EmptyR -> (lr, rr)
+    llr :> m -> let (lm, rm) = T.splitAt (fromIntegral $ n - measure lr) m
+                in (llr |> lm, rm <| rr)
+  where
+    (lr, rr) = split (> n) r
+
+take, drop :: CharOffset -> Rope -> Rope
+take n = fst . splitAt n
+drop n = snd . splitAt n
+
+concat :: Rope -> T.Text
+concat = T.concat . toList
+
+isPrefixOf :: T.Text -> Rope -> Bool
+text `isPrefixOf` rope = case viewl rope of
+  EmptyL -> T.null text
+  chunk :< rope' -> if T.length text < T.length chunk
+                      then text `T.isPrefixOf` chunk
+                      else chunk `T.isPrefixOf` text && (T.drop (T.length chunk) text) `isPrefixOf` rope'