diff --git a/src/Data/Text/Zipper.hs b/src/Data/Text/Zipper.hs
--- a/src/Data/Text/Zipper.hs
+++ b/src/Data/Text/Zipper.hs
@@ -30,6 +30,7 @@
     , insertChar
     , breakLine
     , killToEOL
+    , killToBOL
     , gotoEOL
     , gotoBOL
     , deletePrevChar
@@ -42,6 +43,7 @@
 where
 
 import Control.Applicative ((<$>))
+import Control.DeepSeq
 import Data.Monoid
 import qualified Data.Text as T
 import qualified Data.Vector as V
@@ -61,6 +63,13 @@
        , lineLimit :: Maybe Int
        }
 
+instance (NFData a) => NFData (TextZipper a) where
+    rnf z = (toLeft z) `deepseq`
+            (toRight z) `deepseq`
+            (above z) `deepseq`
+            (below z) `deepseq`
+            ()
+
 -- | Get the line limit, if any, for a zipper.
 getLineLimit :: TextZipper a -> Maybe Int
 getLineLimit = lineLimit
@@ -207,6 +216,12 @@
              }
     | otherwise = tz { toRight = mempty
                      }
+
+-- |Remove all text from the cursor position to the beginning of the
+-- current line.
+killToBOL :: Monoid a => TextZipper a -> TextZipper a
+killToBOL tz = tz { toLeft = mempty
+                  }
 
 -- |Delete the character preceding the cursor position, and move the
 -- cursor backwards by one character.
diff --git a/text-zipper.cabal b/text-zipper.cabal
--- a/text-zipper.cabal
+++ b/text-zipper.cabal
@@ -1,5 +1,5 @@
 name:                text-zipper
-version:             0.4
+version:             0.5
 synopsis:            A text editor zipper library
 description:         This library provides a zipper and API for editing text.
 license:             BSD3
@@ -21,6 +21,8 @@
 
   build-depends:       base < 5,
                        text,
-                       vector
+                       vector,
+                       deepseq
+  ghc-options:         -Wall
   hs-source-dirs:      src
   default-language:    Haskell2010