% ------------------------------------------------------------------------------
-% $Id: PrelList.lhs,v 1.23 2001/02/26 09:29:32 simonpj Exp $
+% $Id: PrelList.lhs,v 1.28 2001/09/26 15:12:37 simonpj Exp $
%
% (c) The University of Glasgow, 1994-2000
%
-- filter, applied to a predicate and a list, returns the list of those
-- elements that satisfy the predicate; i.e.,
-- filter p xs = [ x | x <- xs, p x]
+{-# NOINLINE [1] filter #-}
filter :: (a -> Bool) -> [a] -> [a]
filter = filterList
+{-# INLINE [0] filter #-}
filterFB c p x r | p x = x `c` r
| otherwise = r
[] -> []
x:xs -> scanl f (f q x) xs)
-scanl1 :: (a -> a -> a) -> [a] -> [a]
-scanl1 f (x:xs) = scanl f x xs
-scanl1 _ [] = errorEmptyList "scanl1"
+scanl1 :: (a -> a -> a) -> [a] -> [a]
+scanl1 f (x:xs) = scanl f x xs
+scanl1 _ [] = []
-- foldr, foldr1, scanr, and scanr1 are the right-to-left duals of the
-- above functions.
where qs@(q:_) = scanr f q0 xs
scanr1 :: (a -> a -> a) -> [a] -> [a]
-scanr1 _ [x] = [x]
-scanr1 f (x:xs) = f x q : qs
+scanr1 f [] = []
+scanr1 f [x] = [x]
+scanr1 f (x:xs) = f x q : qs
where qs@(q:_) = scanr1 f xs
-scanr1 _ [] = errorEmptyList "scanr1"
-- iterate f x returns an infinite list of repeated applications of f to x:
-- iterate f x == [x, f x, f (f x), ...]
iterate :: (a -> a) -> a -> [a]
+{-# NOINLINE [1] iterate #-}
iterate = iterateList
iterateFB c f x = x `c` iterateFB c f (f x)
-- repeat x is an infinite list, with x the value of every element.
repeat :: a -> [a]
+{-# NOINLINE [1] repeat #-}
repeat = repeatList
+{-# INLINE [0] repeatFB #-}
repeatFB c x = xs where xs = x `c` xs
+
repeatList x = xs where xs = x : xs
{-# RULES
-- is equivalent to (take n xs, drop n xs).
#ifdef USE_REPORT_PRELUDE
take :: Int -> [a] -> [a]
-take 0 _ = []
+take n _ | n <= 0 = []
take _ [] = []
-take n (x:xs) | n > 0 = x : take (minusInt n 1) xs
-take _ _ = errorNegativeIdx "take"
+take n (x:xs) = x : take (n-1) xs
drop :: Int -> [a] -> [a]
-drop 0 xs = xs
+drop n xs | n <= 0 = xs
drop _ [] = []
-drop n (_:xs) | n > 0 = drop (minusInt n 1) xs
-drop _ _ = errorNegativeIdx "drop"
-
+drop n (_:xs) = drop (n-1) xs
-splitAt :: Int -> [a] -> ([a],[a])
-splitAt 0 xs = ([],xs)
-splitAt _ [] = ([],[])
-splitAt n (x:xs) | n > 0 = (x:xs',xs'') where (xs',xs'') = splitAt (minusInt n 1) xs
-splitAt _ _ = errorNegativeIdx "splitAt"
+splitAt :: Int -> [a] -> ([a],[a])
+splitAt n xs = (take n xs, drop n xs)
#else /* hack away */
take :: Int -> [b] -> [b]
takeUInt :: Int# -> [b] -> [b]
takeUInt n xs
| n >=# 0# = take_unsafe_UInt n xs
- | otherwise = errorNegativeIdx "take"
+ | otherwise = []
take_unsafe_UInt :: Int# -> [b] -> [b]
take_unsafe_UInt 0# _ = []
takeUInt_append :: Int# -> [b] -> [b] -> [b]
takeUInt_append n xs rs
| n >=# 0# = take_unsafe_UInt_append n xs rs
- | otherwise = errorNegativeIdx "take"
+ | otherwise = []
take_unsafe_UInt_append :: Int# -> [b] -> [b] -> [b]
take_unsafe_UInt_append 0# _ rs = rs
drop :: Int -> [b] -> [b]
drop (I# n#) ls
- | n# <# 0# = errorNegativeIdx "drop"
+ | n# <# 0# = []
| otherwise = drop# n# ls
where
drop# :: Int# -> [a] -> [a]
splitAt :: Int -> [b] -> ([b], [b])
splitAt (I# n#) ls
- | n# <# 0# = errorNegativeIdx "splitAt"
+ | n# <# 0# = ([], ls)
| otherwise = splitAt# n# ls
where
splitAt# :: Int# -> [a] -> ([a], [a])
-- List index (subscript) operator, 0-origin
(!!) :: [a] -> Int -> a
#ifdef USE_REPORT_PRELUDE
-(x:_) !! 0 = x
-(_:xs) !! n | n > 0 = xs !! (minusInt n 1)
-(_:_) !! _ = error "Prelude.(!!): negative index"
-[] !! _ = error "Prelude.(!!): index too large"
+xs !! n | n < 0 = error "Prelude.!!: negative index"
+[] !! _ = error "Prelude.!!: index too large"
+(x:_) !! 0 = x
+(_:xs) !! n = xs !! (n-1)
#else
-- HBC version (stolen), then unboxified
-- The semantics is not quite the same for error conditions
zip takes two lists and returns a list of corresponding pairs. If one
input list is short, excess elements of the longer list are discarded.
zip3 takes three lists and returns a list of triples. Zips for larger
-tuples are in the List library
+tuples are in the List module.
\begin{code}
----------------------------------------------
zip :: [a] -> [b] -> [(a,b)]
+{-# NOINLINE [1] zip #-}
zip = zipList
+{-# INLINE [0] zipFB #-}
zipFB c x y r = (x,y) `c` r
\begin{code}
----------------------------------------------
zipWith :: (a->b->c) -> [a]->[b]->[c]
+{-# NOINLINE [1] zipWith #-}
zipWith = zipWithList
-
+{-# INLINE [0] zipWithFB #-}
zipWithFB c f x y r = (x `f` y) `c` r
zipWithList :: (a->b->c) -> [a] -> [b] -> [c]
errorEmptyList fun =
error (prel_list_str ++ fun ++ ": empty list")
-errorNegativeIdx :: String -> a
-errorNegativeIdx fun =
- error (prel_list_str ++ fun ++ ": negative index")
-
prel_list_str :: String
prel_list_str = "Prelude."
\end{code}
projects / ghc-hetmet.git / blobdiff