, reverse -- :: [a] -> [a]
, intersperse -- :: a -> [a] -> [a]
+ , intercalate -- :: [a] -> [[a]] -> [a]
, transpose -- :: [[a]] -> [[a]]
-- * Reducing lists (folds)
, span -- :: (a -> Bool) -> [a] -> ([a], [a])
, break -- :: (a -> Bool) -> [a] -> ([a], [a])
+ , split -- :: Eq a => a -> [a] -> [[a]]
+
, group -- :: Eq a => [a] -> [[a]]
, inits -- :: [a] -> [[a]]
intersperse _ [x] = [x]
intersperse sep (x:xs) = x : sep : intersperse sep xs
+-- | 'intercalate' @xs xss@ is equivalent to @('concat' ('intersperse' xs xss))@.
+-- It inserts the list @xs@ in between the lists in @xss@ and concatenates the
+-- result.
+intercalate :: [a] -> [[a]] -> [a]
+intercalate xs xss = concat (intersperse xs xss)
+
-- | The 'transpose' function transposes the rows and columns of its argument.
-- For example,
--
deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
deleteFirstsBy eq = foldl (flip (deleteBy eq))
+-- | 'split' @x xs@ divides the list @xs@ at every occurrence of @x@ and
+-- removes those occurrences.
+--
+-- Example:
+--
+-- > split 'i' "mississippi" -> ["m","ss","ss","pp",""]
+-- > split 'i' [] -> [""]
+split :: Eq a => a -> [a] -> [[a]]
+split x xs = let (f,r) = break (==x) xs
+ in f : case r of
+ [] -> []
+ (_:ys) -> split x ys
+
-- | The 'group' function takes a list and returns a list of lists such
-- that the concatenation of the result is equal to the argument. Moreover,
-- each sublist in the result contains only equal elements. For example,