Rewrite zipLazy to be warning-free for GHC 6.4

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

diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs
index 59f3b47..8cfdf83 100644 (file)
--- a/compiler/utils/Util.lhs
+++ b/compiler/utils/Util.lhs
@@ -6,6 +6,7 @@
 
 \begin{code}
 module Util (
+        debugIsOn,
 
         -- general list processing
         zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
@@ -73,8 +74,6 @@ module Util (
         Direction(..), reslash,
     ) where
 
--- XXX This define is a bit of a hack, and should be done more nicely
-#define FAST_STRING_NOT_NEEDED 1
 #include "HsVersions.h"
 
 import Panic
@@ -107,6 +106,21 @@ infixr 9 `thenCmp`
 
 %************************************************************************
 %*                                                                      *
+\subsection{-DDEBUG}
+%*                                                                      *
+%************************************************************************
+
+\begin{code}
+debugIsOn :: Bool
+#ifdef DEBUG
+debugIsOn = True
+#else
+debugIsOn = False
+#endif
+\end{code}
+
+%************************************************************************
+%*                                                                      *
 \subsection{A for loop}
 %*                                                                      *
 %************************************************************************
@@ -188,7 +202,12 @@ zipWith4Equal msg _ _  _  _  _  =  panic ("zipWith4Equal: unequal lists:"++msg)
 
 zipLazy :: [a] -> [b] -> [(a,b)]
 zipLazy []     _       = []
-zipLazy (x:xs) ~(y:ys) = (x,y) : zipLazy xs ys
+-- We want to write this, but with GHC 6.4 we get a warning, so it
+-- doesn't validate:
+-- zipLazy (x:xs) ~(y:ys) = (x,y) : zipLazy xs ys
+-- so we write this instead:
+zipLazy (x:xs) zs = let y : ys = zs
+                    in (x,y) : zipLazy xs ys
 \end{code}