+++ /dev/null
-module List (
- delete, deleteBy, (\\), deleteFirsts, deleteFirstsBy,
- elemBy, notElemBy, lookupBy, maximumBy, minimumBy,
- nub, nubBy, partition, sums, products, transpose,
- zip4, zip5, zip6, zip7,
- zipWith4, zipWith5, zipWith6, zipWith7,
- unzip4, unzip5, unzip6, unzip7,
- genericLength, genericDrop, genericTake, genericSplitAt,
- genericReplicate,
- elemIndex, elemIndexBy, intersperse, group, groupBy,
- mapAccumL, mapAccumR,
- inits, tails, subsequences, permutations,
- union, intersect ) where
-
--- delete x removes the first occurrence of x from its list argument.
-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
-
--- list difference (non-associative). In the result of xs \\ ys,
--- the first occurrence of each element of ys in turn (if any)
--- has been removed from xs. Thus, (xs ++ ys) \\ xs == ys.
-(\\) :: (Eq a) => [a] -> [a] -> [a]
-(\\) = foldl (flip delete)
-
--- Alternate name for \\
-deleteFirsts :: (Eq a) => [a] -> [a] -> [a]
-deleteFirsts = (\\)
-
-deleteFirstsBy :: (a -> a -> Bool) -> [a] -> [a] -> [a]
-deleteFirstsBy eq = foldl (flip (deleteBy eq))
-
--- elem, notElem, lookup, maximumBy and minimumBy are in PreludeList
-elemBy, notElemBy :: (a -> a -> Bool) -> a -> [a] -> Bool
-elemBy eq _ [] = False
-elemBy eq x (y:ys) = x `eq` y || elemBy eq x ys
-
-notElemBy eq x xs = not (elemBy eq x xs)
-
-lookupBy :: (a -> a -> Bool) -> a -> [(a, b)] -> Maybe b
-lookupBy eq key [] = Nothing
-lookupBy eq key ((x,y):xys)
- | key `eq` x = Just y
- | otherwise = lookupBy eq key xys
-
-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
-
--- nub (meaning "essence") remove duplicate elements from its list argument.
-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)
-
--- partition takes a predicate and a list and returns a pair of lists:
--- those elements of the argument list that do and do not satisfy the
--- predicate, respectively; i,e,,
--- partition p xs == (filter p xs, filter (not . p) xs).
-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)
-
--- sums and products give a list of running sums or products from
--- a list of numbers. e.g., sums [1,2,3] == [0,1,3,6]
-sums, products :: (Num a) => [a] -> [a]
-sums = scanl (+) 0
-products = scanl (*) 1
-
-transpose :: [[a]] -> [[a]]
-transpose = foldr
- (\xs xss -> zipWith (:) xs (xss ++ repeat []))
- []
-
-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))
- ([],[],[],[],[],[],[])
-
-genericLength :: (Num i) => [b] -> i
-genericLength [] = 0
-genericLength (_:l) = 1 + genericLength l
-
-genericDrop :: (Integral i) => i -> [a] -> [a]
-genericDrop 0 xs = xs
-genericDrop _ [] = []
-genericDrop n (_:xs) | n > 0 = genericDrop (n-1) xs
-genericDrop _ _ = error "List.genericDrop: negative argument"
-
-genericTake :: (Integral i) => i -> [a] -> [a]
-genericTake 0 _ = []
-genericTake _ [] = []
-genericTake n (x:xs) | n > 0 = x : genericTake (n-1) xs
-genericTake _ _ = error "List.genericTake: negative argument"
-
-genericSplitAt :: (Integral i) => i -> [b] -> ([b],[b])
-genericSplitAt 0 xs = ([],xs)
-genericSplitAt _ [] = ([],[])
-genericSplitAt n (x:xs) | n > 0 = (x:xs',xs'') where
- (xs',xs'') = genericSplitAt (n-1) xs
-genericSplitAt _ _ = error "List.genericSplitAt: negative argument"
-
-genericReplicate :: (Integral i) => i -> a -> [a]
-genericReplicate n x = genericTake n (repeat x)
-
--- l !! (elemIndex l x) == x if x `elem` l
-elemIndex :: Eq a => [a] -> a -> Int
-elemIndex = elemIndexBy (==)
-
-elemIndexBy :: (a -> a -> Bool) -> [a] -> a -> Int
-elemIndexBy eq [] x = error "List.elemIndexBy: empty list"
-elemIndexBy eq (x:xs) x' = if x `eq` x' then 0 else 1 + elemIndexBy eq xs x'
-
--- 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
-
-
-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
-
--- intersperse sep inserts sep between the elements of its list argument.
--- e.g. intersperse ',' "abcde" == "a,b,c,d,e"
-intersperse :: a -> [a] -> [a]
-intersperse sep [] = []
-intersperse sep [x] = [x]
-intersperse sep (x:xs) = x : sep : intersperse sep 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
-
--- subsequences xs returns the list of all subsequences of xs.
--- e.g., subsequences "abc" == ["","c","b","bc","a","ac","ab","abc"]
-subsequences :: [a] -> [[a]]
-subsequences [] = [[]]
-subsequences (x:xs) = subsequences xs ++ map (x:) (subsequences xs)
-
--- permutations xs returns the list of all permutations of xs.
--- e.g., permutations "abc" == ["abc","bac","bca","acb","cab","cba"]
-permutations :: [a] -> [[a]]
-permutations [] = [[]]
-permutations (x:xs) = [zs | ys <- permutations xs, zs <- interleave x ys ]
- where interleave :: a -> [a] -> [[a]]
- interleave x [] = [[x]]
- interleave x (y:ys) = [x:y:ys] ++ map (y:) (interleave x ys)
-
-union :: (Eq a) => [a] -> [a] -> [a]
-union xs ys = xs ++ (ys \\ xs)
-
-intersect :: (Eq a) => [a] -> [a] -> [a]
-intersect xs ys = [x | x <- xs, x `elem` ys]
-
-
projects / ghc-hetmet.git / blobdiff