------------------------------------------------------------------------------
--- Standard Library: List operations
---
--- Suitable for use with Hugs 98
------------------------------------------------------------------------------
-
-module List (
- elemIndex, elemIndices,
- find, findIndex, findIndices,
- nub, nubBy, delete, deleteBy, (\\), deleteFirstsBy,
- union, unionBy, intersect, intersectBy,
- intersperse, transpose, partition, group, groupBy,
- inits, tails, isPrefixOf, isSuffixOf,
- mapAccumL, mapAccumR,
- sort, sortBy, insert, insertBy, maximumBy, minimumBy,
- genericLength, genericTake, genericDrop,
- genericSplitAt, genericIndex, genericReplicate,
- zip4, zip5, zip6, zip7,
- zipWith4, zipWith5, zipWith6, zipWith7,
- unzip4, unzip5, unzip6, unzip7, unfoldr,
-
- -- ... and what the Prelude exports
- -- List type: []((:), [])
- (:),
- map, (++), concat, filter,
- head, last, tail, init, null, length, (!!),
- foldl, foldl1, scanl, scanl1, foldr, foldr1, scanr, scanr1,
- iterate, repeat, replicate, cycle,
- take, drop, splitAt, takeWhile, dropWhile, span, break,
- lines, words, unlines, unwords, reverse, and, or,
- any, all, elem, notElem, lookup,
- sum, product, maximum, minimum, concatMap,
- zip, zip3, zipWith, zipWith3, unzip, unzip3
- ) where
-
-import Maybe( listToMaybe )
-
-infix 5 \\
-
-elemIndex :: Eq a => a -> [a] -> Maybe Int
-elemIndex x = findIndex (x ==)
-
-elemIndices :: Eq a => a -> [a] -> [Int]
-elemIndices x = findIndices (x ==)
-
-find :: (a -> Bool) -> [a] -> Maybe a
-find p = listToMaybe . filter p
-
-findIndex :: (a -> Bool) -> [a] -> Maybe Int
-findIndex p = listToMaybe . findIndices p
-
-findIndices :: (a -> Bool) -> [a] -> [Int]
-findIndices p xs = [ i | (x,i) <- zip xs [0..], p x ]
-
-nub :: (Eq a) => [a] -> [a]
-nub = nubBy (==)
-
-nubBy :: (a -> a -> Bool) -> [a] -> [a]
-nubBy eq [] = []
-nubBy eq (x:xs) = x : nubBy eq (filter (\y -> not (eq x y)) xs)
-
-delete :: (Eq a) => a -> [a] -> [a]
-delete = deleteBy (==)
-
-deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
-deleteBy eq x [] = []
-deleteBy eq x (y:ys) = if x `eq` y then ys else y : deleteBy eq x ys
-
-(\\) :: (Eq a) => [a] -> [a] -> [a]
-(\\) = foldl (flip delete)
-
-deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
-deleteFirstsBy eq = foldl (flip (deleteBy eq))
-
-union :: (Eq a) => [a] -> [a] -> [a]
-union = unionBy (==)
-
-unionBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
-unionBy eq xs ys = xs ++ foldl (flip (deleteBy eq)) (nubBy eq ys) xs
-
-intersect :: (Eq a) => [a] -> [a] -> [a]
-intersect = intersectBy (==)
-
-intersectBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
-intersectBy eq xs ys = [x | x <- xs, any (eq x) ys]
-
-intersperse :: a -> [a] -> [a]
-intersperse sep [] = []
-intersperse sep [x] = [x]
-intersperse sep (x:xs) = x : sep : intersperse sep xs
-
-transpose :: [[a]] -> [[a]]
-transpose [] = []
-transpose ([] : xss) = transpose xss
-transpose ((x:xs) : xss) = (x : [h | (h:t) <- xss]) :
- transpose (xs : [ t | (h:t) <- xss])
-
-partition :: (a -> Bool) -> [a] -> ([a],[a])
-partition p xs = foldr select ([],[]) xs
- where select x (ts,fs) | p x = (x:ts,fs)
- | otherwise = (ts,x:fs)
-
--- group splits its list argument into a list of lists of equal, adjacent
--- elements. e.g.,
--- group "Mississippi" == ["M","i","ss","i","ss","i","pp","i"]
-group :: (Eq a) => [a] -> [[a]]
-group = groupBy (==)
-
-groupBy :: (a -> a -> Bool) -> [a] -> [[a]]
-groupBy eq [] = []
-groupBy eq (x:xs) = (x:ys) : groupBy eq zs
- where (ys,zs) = span (eq x) xs
-
--- inits xs returns the list of initial segments of xs, shortest first.
--- e.g., inits "abc" == ["","a","ab","abc"]
-inits :: [a] -> [[a]]
-inits [] = [[]]
-inits (x:xs) = [[]] ++ map (x:) (inits xs)
-
--- tails xs returns the list of all final segments of xs, longest first.
--- e.g., tails "abc" == ["abc", "bc", "c",""]
-tails :: [a] -> [[a]]
-tails [] = [[]]
-tails xxs@(_:xs) = xxs : tails xs
-
-isPrefixOf :: (Eq a) => [a] -> [a] -> Bool
-isPrefixOf [] _ = True
-isPrefixOf _ [] = False
-isPrefixOf (x:xs) (y:ys) = x == y && isPrefixOf xs ys
-
-isSuffixOf :: (Eq a) => [a] -> [a] -> Bool
-isSuffixOf x y = reverse x `isPrefixOf` reverse y
-
-mapAccumL :: (a -> b -> (a, c)) -> a -> [b] -> (a, [c])
-mapAccumL f s [] = (s, [])
-mapAccumL f s (x:xs) = (s'',y:ys)
- where (s', y ) = f s x
- (s'',ys) = mapAccumL f s' xs
-
-mapAccumR :: (a -> b -> (a, c)) -> a -> [b] -> (a, [c])
-mapAccumR f s [] = (s, [])
-mapAccumR f s (x:xs) = (s'', y:ys)
- where (s'',y ) = f s' x
- (s', ys) = mapAccumR f s xs
-
-unfoldr :: (b -> Maybe (a,b)) -> b -> [a]
-unfoldr f b = case f b of Nothing -> []
- Just (a,b) -> a : unfoldr f b
-
-sort :: (Ord a) => [a] -> [a]
-sort = sortBy compare
-
-sortBy :: (a -> a -> Ordering) -> [a] -> [a]
-sortBy cmp = foldr (insertBy cmp) []
-
-insert :: (Ord a) => a -> [a] -> [a]
-insert = insertBy compare
-
-insertBy :: (a -> a -> Ordering) -> a -> [a] -> [a]
-insertBy cmp x [] = [x]
-insertBy cmp x ys@(y:ys')
- = case cmp x y of
- GT -> y : insertBy cmp x ys'
- _ -> x : ys
-
-maximumBy :: (a -> a -> a) -> [a] -> a
-maximumBy max [] = error "List.maximumBy: empty list"
-maximumBy max xs = foldl1 max xs
-
-minimumBy :: (a -> a -> a) -> [a] -> a
-minimumBy min [] = error "List.minimumBy: empty list"
-minimumBy min xs = foldl1 min xs
-
-genericLength :: (Integral a) => [b] -> a
-genericLength [] = 0
-genericLength (x:xs) = 1 + genericLength xs
-
-genericTake :: (Integral a) => a -> [b] -> [b]
-genericTake 0 _ = []
-genericTake _ [] = []
-genericTake n (x:xs)
- | n > 0 = x : genericTake (n-1) xs
- | otherwise = error "List.genericTake: negative argument"
-
-genericDrop :: (Integral a) => a -> [b] -> [b]
-genericDrop 0 xs = xs
-genericDrop _ [] = []
-genericDrop n (_:xs)
- | n > 0 = genericDrop (n-1) xs
- | otherwise = error "List.genericDrop: negative argument"
-
-genericSplitAt :: (Integral a) => a -> [b] -> ([b],[b])
-genericSplitAt 0 xs = ([],xs)
-genericSplitAt _ [] = ([],[])
-genericSplitAt n (x:xs)
- | n > 0 = (x:xs',xs'')
- | otherwise = error "List.genericSplitAt: negative argument"
- where (xs',xs'') = genericSplitAt (n-1) xs
-
-genericIndex :: (Integral a) => [b] -> a -> b
-genericIndex (x:_) 0 = x
-genericIndex (_:xs) n
- | n > 0 = genericIndex xs (n-1)
- | otherwise = error "List.genericIndex: negative argument"
-genericIndex _ _ = error "List.genericIndex: index too large"
-
-genericReplicate :: (Integral a) => a -> b -> [b]
-genericReplicate n x = genericTake n (repeat x)
-
-zip4 :: [a] -> [b] -> [c] -> [d] -> [(a,b,c,d)]
-zip4 = zipWith4 (,,,)
-
-zip5 :: [a] -> [b] -> [c] -> [d] -> [e] -> [(a,b,c,d,e)]
-zip5 = zipWith5 (,,,,)
-
-zip6 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] ->
- [(a,b,c,d,e,f)]
-zip6 = zipWith6 (,,,,,)
-
-zip7 :: [a] -> [b] -> [c] -> [d] -> [e] -> [f] ->
- [g] -> [(a,b,c,d,e,f,g)]
-zip7 = zipWith7 (,,,,,,)
-
-zipWith4 :: (a->b->c->d->e) -> [a]->[b]->[c]->[d]->[e]
-zipWith4 z (a:as) (b:bs) (c:cs) (d:ds)
- = z a b c d : zipWith4 z as bs cs ds
-zipWith4 _ _ _ _ _ = []
-
-zipWith5 :: (a->b->c->d->e->f) ->
- [a]->[b]->[c]->[d]->[e]->[f]
-zipWith5 z (a:as) (b:bs) (c:cs) (d:ds) (e:es)
- = z a b c d e : zipWith5 z as bs cs ds es
-zipWith5 _ _ _ _ _ _ = []
-
-zipWith6 :: (a->b->c->d->e->f->g) ->
- [a]->[b]->[c]->[d]->[e]->[f]->[g]
-zipWith6 z (a:as) (b:bs) (c:cs) (d:ds) (e:es) (f:fs)
- = z a b c d e f : zipWith6 z as bs cs ds es fs
-zipWith6 _ _ _ _ _ _ _ = []
-
-zipWith7 :: (a->b->c->d->e->f->g->h) ->
- [a]->[b]->[c]->[d]->[e]->[f]->[g]->[h]
-zipWith7 z (a:as) (b:bs) (c:cs) (d:ds) (e:es) (f:fs) (g:gs)
- = z a b c d e f g : zipWith7 z as bs cs ds es fs gs
-zipWith7 _ _ _ _ _ _ _ _ = []
-
-unzip4 :: [(a,b,c,d)] -> ([a],[b],[c],[d])
-unzip4 = foldr (\(a,b,c,d) ~(as,bs,cs,ds) ->
- (a:as,b:bs,c:cs,d:ds))
- ([],[],[],[])
-
-unzip5 :: [(a,b,c,d,e)] -> ([a],[b],[c],[d],[e])
-unzip5 = foldr (\(a,b,c,d,e) ~(as,bs,cs,ds,es) ->
- (a:as,b:bs,c:cs,d:ds,e:es))
- ([],[],[],[],[])
-
-unzip6 :: [(a,b,c,d,e,f)] -> ([a],[b],[c],[d],[e],[f])
-unzip6 = foldr (\(a,b,c,d,e,f) ~(as,bs,cs,ds,es,fs) ->
- (a:as,b:bs,c:cs,d:ds,e:es,f:fs))
- ([],[],[],[],[],[])
-
-unzip7 :: [(a,b,c,d,e,f,g)] -> ([a],[b],[c],[d],[e],[f],[g])
-unzip7 = foldr (\(a,b,c,d,e,f,g) ~(as,bs,cs,ds,es,fs,gs) ->
- (a:as,b:bs,c:cs,d:ds,e:es,f:fs,g:gs))
- ([],[],[],[],[],[],[])
-
------------------------------------------------------------------------------