Remove maybePrefixMatch, using stripPrefix instead

[ghc-hetmet.git] / compiler / utils / Util.lhs

diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs
index db6f96a..3de52b6 100644 (file)
--- a/compiler/utils/Util.lhs
+++ b/compiler/utils/Util.lhs
@@ -32,6 +32,7 @@ module Util (
 
         -- * List operations controlled by another list
         takeList, dropList, splitAtList, split,
+        dropTail,
 
         -- * For loop
         nTimes,
@@ -41,7 +42,7 @@ module Util (
 
         -- * Comparisons
         isEqual, eqListBy,
-        thenCmp, cmpList, maybePrefixMatch,
+        thenCmp, cmpList,
         removeSpaces,
 
         -- * Transitive closures
@@ -83,9 +84,8 @@ import System.IO.Unsafe ( unsafePerformIO )
 import Data.IORef       ( readIORef, writeIORef )
 import Data.List        hiding (group)
 
-import qualified Data.List as List ( elem )
 #ifdef DEBUG
-import qualified Data.List as List ( notElem )
+import qualified Data.List as List ( elem, notElem )
 import FastTypes
 #endif
 
@@ -608,6 +608,10 @@ splitAtList (_:xs) (y:ys) = (y:ys', ys'')
     where
       (ys', ys'') = splitAtList xs ys
 
+-- drop from the end of a list
+dropTail :: Int -> [a] -> [a]
+dropTail n = reverse . drop n . reverse
+
 snocView :: [a] -> Maybe ([a],a)
         -- Split off the last element
 snocView [] = Nothing
@@ -660,15 +664,6 @@ cmpList cmp (a:as) (b:bs)
 \end{code}
 
 \begin{code}
--- This (with a more general type) is Data.List.stripPrefix from GHC 6.8.
--- This definition can be removed once we require at least 6.8 to build.
-maybePrefixMatch :: String -> String -> Maybe String
-maybePrefixMatch []    rest = Just rest
-maybePrefixMatch (_:_) []   = Nothing
-maybePrefixMatch (p:pat) (r:rest)
-  | p == r    = maybePrefixMatch pat rest
-  | otherwise = Nothing
-
 removeSpaces :: String -> String
 removeSpaces = reverse . dropWhile isSpace . reverse . dropWhile isSpace
 \end{code}