X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Futils%2FUtil.lhs;h=5cf020f7f56929ed598f33f44977e28e493182b4;hp=4058a97f3661227da681fc024654d51271004ce2;hb=4fa44a3ae9c36222ccb460ba3ed24e46bf7c70ae;hpb=7251944b3932ebcef656efdf201edfd8121aea76

diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs
index 4058a97..5cf020f 100644
--- 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
@@ -64,7 +65,7 @@ module Util (
         doesDirNameExist,
         modificationTimeIfExists,
 
-        global, consIORef,
+        global, consIORef, globalMVar, globalEmptyMVar,
 
         -- * Filenames and paths
         Suffix,
@@ -82,10 +83,10 @@ import Data.IORef       ( IORef, newIORef )
 import System.IO.Unsafe ( unsafePerformIO )
 import Data.IORef       ( readIORef, writeIORef )
 import Data.List        hiding (group)
+import Control.Concurrent.MVar ( MVar, newMVar, newEmptyMVar )
 
-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
 
@@ -107,6 +108,15 @@ infixr 9 `thenCmp`
 %*                                                                      *
 %************************************************************************
 
+These booleans are global constants, set by CPP flags.  They allow us to
+recompile a single module (this one) to change whether or not debug output
+appears. They sometimes let us avoid even running CPP elsewhere.
+
+It's important that the flags are literal constants (True/False). Then,
+with -0, tests of the flags in other modules will simplify to the correct
+branch of the conditional, thereby dropping debug code altogether when
+the flags are off.
+
 \begin{code}
 ghciSupported :: Bool
 #ifdef GHCI
@@ -599,6 +609,10 @@ 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
@@ -651,15 +665,6 @@ 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}
@@ -695,6 +700,14 @@ consIORef var x = do
   writeIORef var (x:xs)
 \end{code}
 
+\begin{code}
+globalMVar :: a -> MVar a
+globalMVar a = unsafePerformIO (newMVar a)
+
+globalEmptyMVar :: MVar a
+globalEmptyMVar = unsafePerformIO newEmptyMVar
+\end{code}
+
 Module names:
 
 \begin{code}