[project @ 2002-11-18 14:25:29 by simonpj]

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

diff --git a/ghc/compiler/utils/Util.lhs b/ghc/compiler/utils/Util.lhs
index 9cc5c58..4949515 100644 (file)
--- a/ghc/compiler/utils/Util.lhs
+++ b/ghc/compiler/utils/Util.lhs
@@ -13,9 +13,8 @@ module Util (
        nOfThem, 
        lengthExceeds, lengthIs, lengthAtLeast, listLengthCmp, atLength,
        isSingleton, only,
-       notNull,
+       notNull, snocView,
 
-       snocView,
        isIn, isn'tIn,
 
        -- for-loop
@@ -263,6 +262,15 @@ notNull :: [a] -> Bool
 notNull [] = False
 notNull _  = True
 
+snocView :: [a] -> Maybe ([a],a)
+       -- Split off the last element
+snocView [] = Nothing
+snocView xs = go [] xs
+           where
+               -- Invariant: second arg is non-empty
+             go acc [x]    = Just (reverse acc, x)
+             go acc (x:xs) = go (x:acc) xs
+
 only :: [a] -> a
 #ifdef DEBUG
 only [a] = a
@@ -271,14 +279,6 @@ only (a:_) = a
 #endif
 \end{code}
 
-\begin{code}
-snocView :: [a] -> ([a], a)    -- Split off the last element
-snocView xs = go xs []
-           where
-             go [x]    acc = (reverse acc, x)
-             go (x:xs) acc = go xs (x:acc)
-\end{code}
-
 Debugging/specialising versions of \tr{elem} and \tr{notElem}
 
 \begin{code}