-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.List
, foldl -- :: (a -> b -> a) -> a -> [b] -> a
, foldl' -- :: (a -> b -> a) -> a -> [b] -> a
, foldl1 -- :: (a -> a -> a) -> [a] -> a
+ , foldl1' -- :: (a -> a -> a) -> [a] -> a
, foldr -- :: (a -> b -> b) -> b -> [a] -> b
, foldr1 -- :: (a -> a -> a) -> [a] -> a
-- ** Predicates
, isPrefixOf -- :: (Eq a) => [a] -> [a] -> Bool
, isSuffixOf -- :: (Eq a) => [a] -> [a] -> Bool
+ , isInfixOf -- :: (Eq a) => [a] -> [a] -> Bool
-- * Searching lists
isSuffixOf :: (Eq a) => [a] -> [a] -> Bool
isSuffixOf x y = reverse x `isPrefixOf` reverse y
+-- | The 'isInfixOf' function takes two lists and returns 'True'
+-- iff the first list is contained, wholly and intact,
+-- anywhere within the second.
+--
+-- Example:
+--
+-- >isInfixOf "Haskell" "I really like Haskell." -> True
+-- >isInfixOf "Ial" "I really like Haskell." -> False
+isInfixOf :: (Eq a) => [a] -> [a] -> Bool
+isInfixOf needle haystack = any (isPrefixOf needle) (tails haystack)
+
-- | The 'nub' function removes duplicate elements from a list.
-- In particular, it keeps only the first occurrence of each element.
-- (The name 'nub' means \`essence\'.)
GT -> y : insertBy cmp x ys'
_ -> x : ys
+#ifdef __GLASGOW_HASKELL__
+
-- | 'maximum' returns the maximum value from a list,
-- which must be non-empty, finite, and of an ordered type.
-- It is a special case of 'Data.List.maximumBy', which allows the
maximum [] = errorEmptyList "maximum"
maximum xs = foldl1 max xs
-{-# RULES "maximumInt" maximum = maximumInt #-}
+{-# RULES
+ "maximumInt" maximum = (strictMaximum :: [Int] -> Int);
+ "maximumInteger" maximum = (strictMaximum :: [Integer] -> Integer)
+ #-}
-- We can't make the overloaded version of maximum strict without
-- changing its semantics (max might not be strict), but we can for
-- the version specialised to 'Int'.
-maximumInt :: [Int] -> Int
-maximumInt [] = errorEmptyList "maximum"
-maximumInt xs = foldl1' max xs
+strictMaximum :: (Ord a) => [a] -> a
+strictMaximum [] = errorEmptyList "maximum"
+strictMaximum xs = foldl1' max xs
-- | 'minimum' returns the minimum value from a list,
-- which must be non-empty, finite, and of an ordered type.
minimum [] = errorEmptyList "minimum"
minimum xs = foldl1 min xs
-{-# RULES "minimumInt" minimum = minimumInt #-}
+{-# RULES
+ "minimumInt" minimum = (strictMinimum :: [Int] -> Int);
+ "minimumInteger" minimum = (strictMinimum :: [Integer] -> Integer)
+ #-}
-minimumInt :: [Int] -> Int
-minimumInt [] = errorEmptyList "minimum"
-minimumInt xs = foldl1' min xs
+strictMinimum :: (Ord a) => [a] -> a
+strictMinimum [] = errorEmptyList "minimum"
+strictMinimum xs = foldl1' min xs
+
+#endif /* __GLASGOW_HASKELL__ */
-- | The 'maximumBy' function takes a comparison function and a list
-- and returns the greatest element of the list by the comparison function.
foldl' f a [] = a
foldl' f a (x:xs) = let a' = f a x in a' `seq` foldl' f a' xs
+#ifdef __GLASGOW_HASKELL__
-- | 'foldl1' is a variant of 'foldl' that has no starting value argument,
-- and thus must be applied to non-empty lists.
foldl1 :: (a -> a -> a) -> [a] -> a
foldl1 f (x:xs) = foldl f x xs
foldl1 _ [] = errorEmptyList "foldl1"
+#endif /* __GLASGOW_HASKELL__ */
-- | A strict version of 'foldl1'
foldl1' :: (a -> a -> a) -> [a] -> a
unwords [w] = w
unwords (w:ws) = w ++ ' ' : unwords ws
#endif
-#endif /* __GLASGOW_HASKELL__ */
+
+#else /* !__GLASGOW_HASKELL__ */
+
+errorEmptyList :: String -> a
+errorEmptyList fun =
+ error ("Prelude." ++ fun ++ ": empty list")
+
+#endif /* !__GLASGOW_HASKELL__ */