X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Flib%2Fstd%2FList.lhs;h=93640a452de9ae08c114cd78b72ba5cca3bccd74;hb=ea138284b7343bb1810cfbd0284a608dc57f7d46;hp=709687a56f45187dcba8f968fd6e6bca6e41c8a2;hpb=d033cb52223c34095c9ab201158b9008bcba9d8b;p=ghc-hetmet.git

diff --git a/ghc/lib/std/List.lhs b/ghc/lib/std/List.lhs
index 709687a..93640a4 100644
--- a/ghc/lib/std/List.lhs
+++ b/ghc/lib/std/List.lhs
@@ -1,8 +1,10 @@
+% -----------------------------------------------------------------------------
+% $Id: List.lhs,v 1.12 2001/06/25 13:13:58 simonpj Exp $
 %
-% (c) The AQUA Project, Glasgow University, 1994-1999
+% (c) The University of Glasgow, 1994-2000
 %
 
-\section[List]{Module @Lhar@}
+\section[List]{Module @List@}
 
 \begin{code}
 module List 
@@ -65,7 +67,7 @@ module List
    , genericIndex      -- :: (Integral a) => [b] -> a -> b
    , genericReplicate  -- :: (Integral a) => a -> b -> [b]
    
-   , unfoldr		-- :: (a -> Maybe (b,a)) -> a -> (a,[b])
+   , unfoldr		-- :: (b -> Maybe (a, b)) -> b -> [a]
 
    , zip4, zip5, zip6, zip7
    , zipWith4, zipWith5, zipWith6, zipWith7
@@ -207,14 +209,18 @@ nubBy eq (x:xs)         =  x : nubBy eq (filter (\ y -> not (eq x y)) xs)
 nubBy eq l              = nubBy' l []
   where
     nubBy' [] _		= []
-    nubBy' (x:xs) ls
-       | elemBy eq x ls = nubBy' xs ls 
-       | otherwise	= x : nubBy' xs (x:ls)
-
---not exported:
-elemBy :: (a -> a -> Bool) -> a -> [a] -> Bool
-elemBy _  _ []		=  False
-elemBy eq x (y:ys)	=  x `eq` y || elemBy eq x ys
+    nubBy' (y:ys) xs
+       | elem_by eq y xs = nubBy' ys xs 
+       | otherwise	 = y : nubBy' ys (y:xs)
+
+-- Not exported:
+-- Note that we keep the call to `eq` with arguments in the
+-- same order as in the reference implementation
+-- 'xs' is the list of things we've seen so far, 
+-- 'y' is the potential new element
+elem_by :: (a -> a -> Bool) -> a -> [a] -> Bool
+elem_by _  _ []		=  False
+elem_by eq y (x:xs)	=  x `eq` y || elem_by eq y xs
 #endif