{-# LANGUAGE UndecidableInstances, OverlappingInstances, FlexibleInstances, MultiParamTypeClasses, TemplateHaskell, RankNTypes, FunctionalDependencies, DeriveDataTypeable, GADTs, CPP, ScopedTypeVariables #-} {- | An efficient implementation of queryable sets. Assume you have a type like: > data Entry = Entry Author [Author] Updated Id Content > newtype Updated = Updated EpochTime > newtype Id = Id Int64 > newtype Content = Content String > newtype Author = Author Email > type Email = String 1. Decide what parts of your type you want indexed and make your type an instance of 'Indexable'. Use 'ixFun' and 'ixGen' to build indexes: > instance Indexable Entry where > empty = ixSet > [ ixGen (Proxy :: Proxy Author) -- out of order > , ixGen (Proxy :: Proxy Id) > , ixGen (Proxy :: Proxy Updated) > , ixGen (Proxy :: Proxy Test) -- bogus index > ] 3. Use 'insert', 'delete', 'updateIx', 'deleteIx' and 'empty' to build up an 'IxSet' collection: > entries = foldr insert empty [e1,e2,e3,e4] > entries' = foldr delete entries [e1,e3] > entries'' = update e4 e5 entries 4. Use the query functions below to grab data from it: > entries @= (Author "john@doe.com") @< (Updated t1) Statement above will find all items in entries updated earlier than @t1@ by @john\@doe.com@. 5. Text index If you want to do add a text index create a calculated index. Then if you want all entries with either @word1@ or @word2@, you change the instance to: > getWords (Entry _ _ _ _ (Content s)) = map Word $ words s > > instance Indexable Entry where > empty = ixSet [ ... > , ixFun getWords > ] Now you can do this query to find entries with any of the words: > entries @+ [Word "word1", Word "word2"] And if you want all entries with both: > entries @* [Word "word1", Word "word2"] 6. Find only the first author If an @Entry@ has multiple authors and you want to be able to query on the first author only, define a @FirstAuthor@ datatype and create an index with this type. Now you can do: > newtype FirstAuthor = FirstAuthor Email > > getFirstAuthor (Entry author _ _ _ _) = [FirstAuthor author] > > instance Indexable Entry where > ... > empty = ixSet [ ... > , ixFun getFirstAuthor > ] > > entries @= (FirstAuthor "john@doe.com") -- guess what this does -} module Data.IxSet ( -- * Set type IxSet, Indexable(..), Proxy(..), noCalcs, inferIxSet, ixSet, ixFun, ixGen, -- * Changes to set IndexOp, change, insert, delete, updateIx, deleteIx, -- * Creation fromSet, fromList, -- * Conversion toSet, toList, toAscList, toDescList, getOne, getOneOr, -- * Size checking size, null, -- * Set operations (&&&), (|||), union, intersection, -- * Indexing (@=), (@<), (@>), (@<=), (@>=), (@><), (@>=<), (@><=), (@>=<=), (@+), (@*), getOrd, getOrd2, getEQ, getLT, getGT, getLTE, getGTE, getRange, groupBy, groupAscBy, groupDescBy, -- * Index creation helpers flatten, flattenWithCalcs, -- * Debugging and optimization stats ) where import Prelude hiding (null) import Control.Arrow (first, second) import Data.Generics (Data, gmapQ) import qualified Data.Generics.SYB.WithClass.Basics as SYBWC import qualified Data.IxSet.Ix as Ix import Data.IxSet.Ix (Ix(Ix)) import qualified Data.List as List import Data.Map (Map) import qualified Data.Map as Map import Data.Maybe (fromMaybe) import Data.Monoid (Monoid(mempty, mappend)) import Data.SafeCopy (SafeCopy(..), contain, safeGet, safePut) import Data.Set (Set) import qualified Data.Set as Set import Data.Typeable (Typeable, cast, typeOf) import Language.Haskell.TH as TH import Data.Semigroup ------------------------------------------------- -- Type proxies data Proxy a = Proxy mkProxy :: a -> Proxy a mkProxy _ = Proxy asProxyType :: a -> Proxy a -> a asProxyType a _ = a -- the core datatypes -- | Set with associated indexes. data IxSet a = IxSet [Ix a] deriving (Data, Typeable) -- | Create an 'IxSet' using a list of indexes. Typically used to -- create the 'empty' method for an 'Indexable' instance. -- -- The list elements are generally created by using the 'ixFun' and -- 'ixGen' helper functions. -- -- > instance Indexable Type where -- > empty = ixSet [ ... -- > , ixFun getIndex1 -- > , ixGen (Proxy :: Proxy Index2Type) -- > ] -- -- Every value in the 'IxSet' must be reachable by the first index in this -- list, or you'll get a runtime error. ixSet :: [Ix a] -> IxSet a ixSet = IxSet -- | Create a functional index. Provided function should return a list -- of indexes where the value should be found. -- -- > getIndexes value = [...indexes...] -- -- > instance Indexable Type where -- > empty = ixSet [ ixFun getIndexes ] -- -- This is the recommended way to create indexes. ixFun :: forall a b . (Ord b,Typeable b) => (a -> [b]) -> Ix a ixFun f = Ix Map.empty f -- | Create a generic index. Provided example is used only as type source -- so you may use a 'Proxy'. This uses flatten to traverse values using -- their 'Data' instances. -- -- > instance Indexable Type where -- > empty = ixSet [ ixGen (Proxy :: Proxy Type) ] -- -- In production systems consider using 'ixFun' in place of 'ixGen' as -- the former one is much faster. ixGen :: forall a b . (Data a,Ord b,Typeable b) => Proxy b -> Ix a ixGen _example = ixFun (flatten :: a -> [b]) showTypeOf :: (Typeable a) => a -> String showTypeOf x = showsPrec 11 (typeOf x) [] instance (Eq a,Ord a,Typeable a) => Eq (IxSet a) where IxSet (Ix a _:_) == IxSet (Ix b _:_) = case cast b of Just b' -> a==b' Nothing -> error "trying to compare two sets with different types of first indexes, this is a bug in the library" _ == _ = error "comparing sets without indexes, this is a bug in the library" instance (Eq a,Ord a,Typeable a) => Ord (IxSet a) where compare a b = compare (toSet a) (toSet b) {- FIXME instance Version (IxSet a) instance (Serialize a, Ord a, Typeable a, Indexable a) => Serialize (IxSet a) where putCopy = contain . safePut . toList getCopy = contain $ liftM fromList safeGet -} instance (SafeCopy a, Ord a, Typeable a, Indexable a) => SafeCopy (IxSet a) where putCopy = contain . safePut . toList getCopy = contain $ fmap fromList safeGet instance ( SYBWC.Data ctx a , SYBWC.Data ctx [a] , SYBWC.Sat (ctx (IxSet a)) , SYBWC.Sat (ctx [a]) , SYBWC.Typeable IxSet , Indexable a , Data a , Ord a ) => SYBWC.Data ctx (IxSet a) where gfoldl _ f z ixset = z fromList `f` toList ixset toConstr _ (IxSet _) = ixSetConstr gunfold _ k z c = case SYBWC.constrIndex c of 1 -> k (z fromList) _ -> error "IxSet.SYBWC.Data.gunfold unexpected match" dataTypeOf _ _ = ixSetDataType ixSetConstr :: SYBWC.Constr ixSetConstr = SYBWC.mkConstr ixSetDataType "IxSet" [] SYBWC.Prefix ixSetDataType :: SYBWC.DataType ixSetDataType = SYBWC.mkDataType "IxSet" [ixSetConstr] {- FIXME instance (Indexable a, Ord a,Data a, Default a) => Default (IxSet a) where defaultValue = empty -} instance (Ord a,Show a) => Show (IxSet a) where showsPrec prec = showsPrec prec . toSet instance (Ord a,Read a,Typeable a,Indexable a) => Read (IxSet a) where readsPrec n = map (first fromSet) . readsPrec n {- | Defines objects that can be members of 'IxSet'. -} class Indexable a where -- | Defines what an empty 'IxSet' for this particular type should look -- like. It should have all necessary indexes. Use the 'ixSet' -- function to create the set and fill it in with 'ixFun' and 'ixGen'. empty :: IxSet a -- | Function to be used for 'calcs' in 'inferIxSet' when you don't -- want any calculated values. noCalcs :: t -> () noCalcs _ = () {- | Template Haskell helper function for automatically building an 'Indexable' instance from a data type, e.g. > data Foo = Foo Int String and > $(inferIxSet "FooDB" ''Foo 'noCalcs [''Int,''String]) will build a type synonym > type FooDB = IxSet Foo with @Int@ and @String@ as indexes. /WARNING/: The type specified as the first index must be a type which appears in all values in the 'IxSet' or 'toList', 'toSet' and serialization will not function properly. You will be warned not to do this with a runtime error. You can always use the element type itself. For example: > $(inferIxSet "FooDB" ''Foo 'noCalcs [''Foo, ''Int, ''String]) -} inferIxSet :: String -> TH.Name -> TH.Name -> [TH.Name] -> Q [Dec] inferIxSet _ _ _ [] = error "inferIxSet needs at least one index" inferIxSet ixset typeName calName entryPoints = do calInfo <- reify calName typeInfo <- reify typeName let (context,binders) = case typeInfo of #if MIN_VERSION_template_haskell(2,11,0) TyConI (DataD ctxt _ nms _ _ _) -> (ctxt,nms) TyConI (NewtypeD ctxt _ nms _ _ _) -> (ctxt,nms) #else TyConI (DataD ctxt _ nms _ _) -> (ctxt,nms) TyConI (NewtypeD ctxt _ nms _ _) -> (ctxt,nms) #endif TyConI (TySynD _ nms _) -> ([],nms) _ -> error "IxSet.inferIxSet typeInfo unexpected match" names = map tyVarBndrToName binders typeCon = List.foldl' appT (conT typeName) (map varT names) #if MIN_VERSION_template_haskell(2,4,0) mkCtx = classP #else -- mkType :: Name -> [TypeQ] -> TypeQ mkType con = foldl appT (conT con) mkCtx = mkType #endif dataCtxConQ = [mkCtx ''Data [varT name] | name <- names] fullContext = do dataCtxCon <- sequence dataCtxConQ return (context ++ dataCtxCon) case calInfo of #if MIN_VERSION_template_haskell(2,11,0) VarI _ t _ -> #else VarI _ t _ _ -> #endif let calType = getCalType t getCalType (ForallT _names _ t') = getCalType t' getCalType (AppT (AppT ArrowT _) t') = t' getCalType t' = error ("Unexpected type in getCalType: " ++ pprint t') mkEntryPoint n = (conE 'Ix) `appE` (sigE (varE 'Map.empty) (forallT binders (return context) $ appT (appT (conT ''Map) (conT n)) (appT (conT ''Set) typeCon))) `appE` (varE 'flattenWithCalcs `appE` varE calName) in do i <- instanceD (fullContext) (conT ''Indexable `appT` typeCon) [valD (varP 'empty) (normalB [| ixSet $(listE (map mkEntryPoint entryPoints)) |]) []] let ixType = appT (conT ''IxSet) typeCon ixType' <- tySynD (mkName ixset) binders ixType return $ [i, ixType'] -- ++ d _ -> error "IxSet.inferIxSet calInfo unexpected match" -- | Version of 'instanceD' that takes in a Q [Dec] instead of a [Q Dec] -- and filters out signatures from the list of declarations. instanceD' :: CxtQ -> TypeQ -> Q [Dec] -> DecQ instanceD' ctxt ty decs = do decs' <- decs let decs'' = filter (not . isSigD) decs' instanceD ctxt ty (map return decs'') -- | Returns true if the Dec matches a SigD constructor. isSigD :: Dec -> Bool isSigD (SigD _ _) = True isSigD _ = False #if MIN_VERSION_template_haskell(2,4,0) tyVarBndrToName :: TyVarBndr -> Name tyVarBndrToName (PlainTV nm) = nm tyVarBndrToName (KindedTV nm _) = nm #else tyVarBndrToName :: a -> a tyVarBndrToName = id #endif -- modification operations type IndexOp = forall k a. (Ord k,Ord a) => k -> a -> Map k (Set a) -> Map k (Set a) -- | Generically traverses the argument to find all occurences of -- values of type @b@ and returns them as a list. -- -- This function properly handles 'String' as 'String' not as @['Char']@. flatten :: (Typeable a, Data a, Typeable b) => a -> [b] flatten x = case cast x of Just y -> case cast (y :: String) of Just v -> [v] Nothing -> [] Nothing -> case cast x of Just v -> v : concat (gmapQ flatten x) Nothing -> concat (gmapQ flatten x) -- | Generically traverses the argument and calculated values to find -- all occurences of values of type @b@ and returns them as a -- list. Equivalent to: -- -- > flatten (x,calcs x) -- -- This function properly handles 'String' as 'String' not as @['Char']@. flattenWithCalcs :: (Data c,Typeable a, Data a, Typeable b) => (a -> c) -> a -> [b] flattenWithCalcs calcs x = flatten (x,calcs x) -- | Higher order operator for modifying 'IxSet's. Use this when your -- final function should have the form @a -> 'IxSet' a -> 'IxSet' a@, -- e.g. 'insert' or 'delete'. change :: (Typeable a,Indexable a,Ord a) => IndexOp -> a -> IxSet a -> IxSet a change op x (IxSet indexes) = IxSet v where v = zipWith update (True:repeat False) indexes update firstindex (Ix index flatten2) = Ix index' flatten2 where key = (undefined :: Map key (Set a) -> key) index ds = flatten2 x ii m dkey = op dkey x m index' = if firstindex && List.null ds then error $ "Happstack.Data.IxSet.change: all values must appear in first declared index " ++ showTypeOf key ++ " of " ++ showTypeOf x else List.foldl' ii index ds -- handle multiple values insertList :: (Typeable a,Indexable a,Ord a) => [a] -> IxSet a -> IxSet a insertList xs (IxSet indexes) = IxSet v where v = zipWith update (True:repeat False) indexes update firstindex (Ix index flatten2) = Ix index' flatten2 where key = (undefined :: Map key (Set a) -> key) index flattencheck x | firstindex = case flatten2 x of [] -> error $ "Happstack.Data.IxSet.change: all values must appear in first declared index " ++ showTypeOf key ++ " of " ++ showTypeOf x res -> res | otherwise = flatten2 x dss = [(k,x) | x <- xs, k <- flattencheck x] index' = Ix.insertList dss index insertMapOfSets :: (Typeable a, Ord a,Indexable a,Typeable key,Ord key) => Map key (Set a) -> IxSet a -> IxSet a insertMapOfSets originalindex (IxSet indexes) = IxSet v where v = map update indexes xs = concatMap Set.toList (Map.elems originalindex) update (Ix index flatten2) = Ix index' flatten2 where dss = [(k,x) | x <- xs, k <- flatten2 x] {- We try to be really clever here. The originalindex is a Map of Sets from original index. We want to reuse it as much as possible. If there was a guarantee that each element is present at at most one index we could reuse originalindex as it is. But there can be more, so we need to add remaining ones. Anyway we try to reuse old structure and keep new allocations low as much as possible. -} index' = case cast originalindex of Just originalindex' -> let dssf = filter (\(k,_v) -> not (Map.member k originalindex')) dss in Ix.insertList dssf originalindex' Nothing -> Ix.insertList dss index -- | Inserts an item into the 'IxSet'. If your data happens to have -- a primary key this function might not be what you want. See -- 'updateIx'. insert :: (Typeable a, Ord a,Indexable a) => a -> IxSet a -> IxSet a insert = change Ix.insert -- | Removes an item from the 'IxSet'. delete :: (Typeable a, Ord a,Indexable a) => a -> IxSet a -> IxSet a delete = change Ix.delete -- | Will replace the item with index k. Only works if there is at -- most one item with that index in the 'IxSet'. Will not change -- 'IxSet' if you have more then 1 item with given index. updateIx :: (Indexable a, Ord a, Typeable a, Typeable k) => k -> a -> IxSet a -> IxSet a updateIx i new ixset = insert new $ maybe ixset (flip delete ixset) $ getOne $ ixset @= i -- | Will delete the item with index k. Only works if there is at -- most one item with that index in the 'IxSet'. Will not change -- 'IxSet' if you have more then 1 item with given index. deleteIx :: (Indexable a, Ord a, Typeable a, Typeable k) => k -> IxSet a -> IxSet a deleteIx i ixset = maybe ixset (flip delete ixset) $ getOne $ ixset @= i -- conversion operations -- | Converts an 'IxSet' to a 'Set' of its elements. toSet :: Ord a => IxSet a -> Set a toSet (IxSet (Ix ix _:_)) = List.foldl' Set.union Set.empty (Map.elems ix) toSet (IxSet []) = Set.empty -- | Converts a 'Set' to an 'IxSet'. fromSet :: (Indexable a, Ord a, Typeable a) => Set a -> IxSet a fromSet = fromList . Set.toList -- | Converts a list to an 'IxSet'. fromList :: (Indexable a, Ord a, Typeable a) => [a] -> IxSet a fromList list = insertList list empty -- | Returns the number of unique items in the 'IxSet'. size :: Ord a => IxSet a -> Int size = Set.size . toSet -- | Converts an 'IxSet' to its list of elements. toList :: Ord a => IxSet a -> [a] toList = Set.toList . toSet -- | Converts an 'IxSet' to its list of elements. -- -- List will be sorted in ascending order by the index 'k'. -- -- The list may contain duplicate entries if a single value produces multiple keys. toAscList :: forall k a. (Indexable a, Typeable a, Typeable k) => Proxy k -> IxSet a -> [a] toAscList _ ixset = concatMap snd (groupAscBy ixset :: [(k, [a])]) -- | Converts an 'IxSet' to its list of elements. -- -- List will be sorted in descending order by the index 'k'. -- -- The list may contain duplicate entries if a single value produces multiple keys. toDescList :: forall k a. (Indexable a, Typeable a, Typeable k) => Proxy k -> IxSet a -> [a] toDescList _ ixset = concatMap snd (groupDescBy ixset :: [(k, [a])]) -- | If the 'IxSet' is a singleton it will return the one item stored in it. -- If 'IxSet' is empty or has many elements this function returns 'Nothing'. getOne :: Ord a => IxSet a -> Maybe a getOne ixset = case toList ixset of [x] -> Just x _ -> Nothing -- | Like 'getOne' with a user-provided default. getOneOr :: Ord a => a -> IxSet a -> a getOneOr def = fromMaybe def . getOne -- | Return 'True' if the 'IxSet' is empty, 'False' otherwise. null :: IxSet a -> Bool null (IxSet (Ix ix _:_)) = Map.null ix null (IxSet []) = True -- set operations -- | An infix 'intersection' operation. (&&&) :: (Ord a, Typeable a, Indexable a) => IxSet a -> IxSet a -> IxSet a (&&&) = intersection -- | An infix 'union' operation. (|||) :: (Ord a, Typeable a, Indexable a) => IxSet a -> IxSet a -> IxSet a (|||) = union infixr 5 &&& infixr 5 ||| -- | Takes the union of the two 'IxSet's. union :: (Ord a, Typeable a, Indexable a) => IxSet a -> IxSet a -> IxSet a union (IxSet x1) (IxSet x2) = IxSet indexes' where indexes' = zipWith union' x1 x2 union' (Ix a f) (Ix b _) = case cast b of Nothing -> error "IxSet.union: indexes out of order" Just b' -> Ix (Ix.union a b') f -- | Takes the intersection of the two 'IxSet's. intersection :: (Ord a, Typeable a, Indexable a) => IxSet a -> IxSet a -> IxSet a intersection (IxSet x1) (IxSet x2) = IxSet indexes' where indexes' = zipWith intersection' x1 x2 intersection' (Ix a f) (Ix b _) = case cast b of Nothing -> error "IxSet.intersection: indexes out of order" Just b' -> Ix (Ix.intersection a b') f -- query operators -- | Infix version of 'getEQ'. (@=) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> k -> IxSet a ix @= v = getEQ v ix -- | Infix version of 'getLT'. (@<) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> k -> IxSet a ix @< v = getLT v ix -- | Infix version of 'getGT'. (@>) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> k -> IxSet a ix @> v = getGT v ix -- | Infix version of 'getLTE'. (@<=) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> k -> IxSet a ix @<= v = getLTE v ix -- | Infix version of 'getGTE'. (@>=) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> k -> IxSet a ix @>= v = getGTE v ix -- | Returns the subset with indexes in the open interval (k,k). (@><) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> (k, k) -> IxSet a ix @>< (v1,v2) = getLT v2 $ getGT v1 ix -- | Returns the subset with indexes in [k,k). (@>=<) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> (k, k) -> IxSet a ix @>=< (v1,v2) = getLT v2 $ getGTE v1 ix -- | Returns the subset with indexes in (k,k]. (@><=) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> (k, k) -> IxSet a ix @><= (v1,v2) = getLTE v2 $ getGT v1 ix -- | Returns the subset with indexes in [k,k]. (@>=<=) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> (k, k) -> IxSet a ix @>=<= (v1,v2) = getLTE v2 $ getGTE v1 ix -- | Creates the subset that has an index in the provided list. (@+) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> [k] -> IxSet a ix @+ list = List.foldl' union empty $ map (ix @=) list -- | Creates the subset that matches all the provided indexes. (@*) :: (Indexable a, Typeable a, Ord a, Typeable k) => IxSet a -> [k] -> IxSet a ix @* list = List.foldl' intersection ix $ map (ix @=) list -- | Returns the subset with an index equal to the provided key. The -- set must be indexed over key type, doing otherwise results in -- runtime error. getEQ :: (Indexable a, Typeable a, Ord a, Typeable k) => k -> IxSet a -> IxSet a getEQ = getOrd EQ -- | Returns the subset with an index less than the provided key. The -- set must be indexed over key type, doing otherwise results in -- runtime error. getLT :: (Indexable a, Typeable a, Ord a, Typeable k) => k -> IxSet a -> IxSet a getLT = getOrd LT -- | Returns the subset with an index greater than the provided key. -- The set must be indexed over key type, doing otherwise results in -- runtime error. getGT :: (Indexable a, Typeable a, Ord a, Typeable k) => k -> IxSet a -> IxSet a getGT = getOrd GT -- | Returns the subset with an index less than or equal to the -- provided key. The set must be indexed over key type, doing -- otherwise results in runtime error. getLTE :: (Indexable a, Typeable a, Ord a, Typeable k) => k -> IxSet a -> IxSet a getLTE = getOrd2 True True False -- | Returns the subset with an index greater than or equal to the -- provided key. The set must be indexed over key type, doing -- otherwise results in runtime error. getGTE :: (Indexable a, Typeable a, Ord a, Typeable k) => k -> IxSet a -> IxSet a getGTE = getOrd2 False True True -- | Returns the subset with an index within the interval provided. -- The bottom of the interval is closed and the top is open, -- i. e. [k1;k2). The set must be indexed over key type, doing -- otherwise results in runtime error. getRange :: (Indexable a, Typeable k, Ord a, Typeable a) => k -> k -> IxSet a -> IxSet a getRange k1 k2 ixset = getGTE k1 (getLT k2 ixset) -- | Returns lists of elements paired with the indexes determined by -- type inference. groupBy :: (Typeable k,Typeable t) => IxSet t -> [(k, [t])] groupBy (IxSet indexes) = collect indexes where collect [] = [] -- FIXME: should be an error collect (Ix index _:is) = maybe (collect is) f (cast index) f = map (second Set.toList) . Map.toList -- | Returns lists of elements paired with the indexes determined by -- type inference. -- -- The resulting list will be sorted in ascending order by 'k'. -- The values in '[t]' will be sorted in ascending order as well. groupAscBy :: (Typeable k,Typeable t) => IxSet t -> [(k, [t])] groupAscBy (IxSet indexes) = collect indexes where collect [] = [] -- FIXME: should be an error collect (Ix index _:is) = maybe (collect is) f (cast index) f = map (second Set.toAscList) . Map.toAscList -- | Returns lists of elements paired with the indexes determined by -- type inference. -- -- The resulting list will be sorted in descending order by 'k'. -- -- NOTE: The values in '[t]' are currently sorted in ascending -- order. But this may change if someone bothers to add -- 'Set.toDescList'. So do not rely on the sort order of '[t]'. groupDescBy :: (Typeable k,Typeable t) => IxSet t -> [(k, [t])] groupDescBy (IxSet indexes) = collect indexes where collect [] = [] -- FIXME: should be an error collect (Ix index _:is) = maybe (collect is) f (cast index) f = map (second Set.toAscList) . Map.toDescList --query impl function -- | A function for building up selectors on 'IxSet's. Used in the -- various get* functions. The set must be indexed over key type, -- doing otherwise results in runtime error. getOrd :: (Indexable a, Ord a, Typeable a, Typeable k) => Ordering -> k -> IxSet a -> IxSet a getOrd LT = getOrd2 True False False getOrd EQ = getOrd2 False True False getOrd GT = getOrd2 False False True -- | A function for building up selectors on 'IxSet's. Used in the -- various get* functions. The set must be indexed over key type, -- doing otherwise results in runtime error. getOrd2 :: (Indexable a, Ord a, Typeable a, Typeable k) => Bool -> Bool -> Bool -> k -> IxSet a -> IxSet a getOrd2 inclt inceq incgt v ixset@(IxSet indexes) = collect indexes where collect [] = error $ "IxSet: there is no index " ++ showTypeOf v ++ " in " ++ showTypeOf ixset collect (Ix index _:is) = maybe (collect is) f $ cast v where f v'' = insertMapOfSets result empty where (lt',eq',gt') = Map.splitLookup v'' index ltgt = Map.unionWith Set.union lt gt result = case eq of Just eqset -> Map.insertWith Set.union v'' eqset ltgt Nothing -> ltgt lt = if inclt then lt' else Map.empty gt = if incgt then gt' else Map.empty eq = if inceq then eq' else Nothing {-- Optimization todo: * can we avoid rebuilding the collection every time we query? does laziness take care of everything? * nicer operators? * nice way to do updates that doesn't involve reinserting the entire data * can we index on xpath rather than just type? --} instance (Indexable a, Typeable a, Ord a) => Semigroup (IxSet a) where (<>) = union instance (Indexable a, Typeable a, Ord a) => Monoid (IxSet a) where mempty = empty mappend = union -- | Statistics about 'IxSet'. This function returns quadruple -- consisting of 1. total number of elements in the set 2. number of -- declared indexes 3. number of keys in all indexes 4. number of -- values in all keys in all indexes. This can aid you in debugging -- and optimisation. stats :: (Ord a) => IxSet a -> (Int,Int,Int,Int) stats (IxSet indexes) = (no_elements,no_indexes,no_keys,no_values) where no_elements = size (IxSet indexes) no_indexes = length indexes no_keys = sum [Map.size m | Ix m _ <- indexes] no_values = sum [sum [Set.size s | s <- Map.elems m] | Ix m _ <- indexes]