Revert "Use TX.span to implement lines'"

src/Yi/Rope.hs

@@ -69,7 +69,6 @@ import qualified Data.ByteString.Lazy as BSL
 import           Data.Char (isSpace)
 import qualified Data.FingerTree as T
 import           Data.FingerTree hiding (null, empty, reverse, split)
-import           Data.Function (fix)
 import qualified Data.List as L (foldl')
 import           Data.Maybe
 import           Data.Monoid
@@ -583,15 +582,13 @@ lines = fmap fromText . TX.lines . toText
 --
 -- > 'toText' . 'concat' . 'lines'' ≡ 'toText'
 --
+-- but the underlying structure might change: notably, chunks will
+-- most likely change sizes.
 lines' :: YiString -> [YiString]
-lines' = splitByKeepingDelim '\n'
-
-splitByKeepingDelim :: Char -> YiString -> [YiString]
-splitByKeepingDelim x = fmap fromText . fix go x . toText
-  where
-    go :: (Char -> TX.Text -> [TX.Text]) -> Char -> TX.Text -> [TX.Text]
-    go _ c (TX.span (/=c) -> (_, TX.null -> True)) = []
-    go f c (TX.span (/=c) -> (a,b)) = a `TX.snoc` c : f c (TX.tail b)
+lines' t = let (YiString f, YiString s) = splitAtLine' 0 t
+           in if T.null s
+              then if T.null f then [] else [YiString f]
+              else YiString f : lines' (YiString s)
 
 -- | Joins up lines by a newline character. It does not leave a
 -- newline after the last line. If you want a more classical

test/Yi/RopeSpec.hs

@@ -37,6 +37,8 @@ spec = modifyMaxSize (const 1000) $ do
     prop "R.length ~ T.length" $ R.length `isLike` T.length
     prop "R.null ~ T.null" $ R.null `isLike` T.null
     prop "R.countNewLines ~ T.count \\n" $ R.countNewLines `isLike` T.count "\n"
+    prop "R.concat . R.lines' = id" $ (R.toText . R.concat . R.lines') `isLike` id
+    prop "R.lines ~ T.lines" $ (fmap R.toText . R.lines) `isLike` T.lines
     prop "R.empty ~ T.empty" $ R.toText R.empty `shouldBe` T.empty
     prop "fst . R.splitAt ~ fst . T.splitAt" $ \i ->
       fst . R.splitAt i `isLikeT` fst . T.splitAt i