{- |

Module : $Header$

Copyright : (c) Uni Bremen 2006

License : similar to LGPL, see HetCATS/LICENSE.txt or LIZENZ.txt

Maintainer : maeder@tzi.de

Stability : provisional

Portability : portable

injective maps

-}

module Common.InjMap

( InjMap

, empty

, insert

, delete

, transpose

, lookupWithA

, lookupWithB

, getAToB

, getBToA

)

where

import qualified Common.Lib.Map as Map

-- * the data type of injective map

data InjMap a b = InjMap (Map.Map a b) (Map.Map b a) deriving Show

-- * the visible interface

-- | gets an empty injective map

empty :: InjMap a b

empty = InjMap Map.empty Map.empty

-- | insert a pair to the given injective map. The existed key and the corresponding content would be overridden

insert :: (Ord a, Ord b) => a -> b -> InjMap a b -> InjMap a b

--insert a b (InjMap m n) = InjMap (Map.insert a b m) (Map.insert b a n)

insert a b (InjMap m n) = case (Map.lookup a m) of

Just x -> insert a b (delete a x (InjMap m n))

Nothing -> case (Map.lookup b n) of

Just y -> insert a b (delete y b (InjMap m n))

Nothing -> InjMap (Map.insert a b m) (Map.insert b a n)

-- | delete the pair with the given keys in the injective map.

delete :: (Ord a, Ord b) => a -> b -> InjMap a b -> InjMap a b

delete a b (InjMap m n) = InjMap (Map.delete a m) (Map.delete b n)

-- | transposing :)

transpose :: InjMap a b -> InjMap b a

transpose (InjMap n m) = (InjMap m n)

-- | look up the content with the given key in the direction of a->b in the injective map

lookupWithA :: (Ord a, Ord b) => a -> InjMap a b -> Maybe b

lookupWithA x (InjMap m n) = case (Map.lookup x m) of

Just y ->

case (Map.lookup y n) of

Just temp ->

if(temp==x) then Just y

else error "Common.InjMap.lookupWithA: the injectivity is destroyed"

Nothing -> error "Common.InjMap.lookupWithA: the inijectivity is destroyed"

Nothing -> Nothing

-- | look up the content with the given key in the direction of b->a in the injective map

lookupWithB :: (Ord a, Ord b) => b -> InjMap a b -> Maybe a

lookupWithB y (InjMap m n) = case (Map.lookup y n) of

Just x ->

case (Map.lookup x m) of

Just temp ->

if(temp==y) then Just x

else error "InjMap.lookupWithA: the injectivity is destroyed"

Nothing -> error "InjMap.lookupWithB: the inijectivity is destroyed"

Nothing -> Nothing

-- | get the part of direction a->b in the map

getAToB :: (Ord a, Ord b) => InjMap a b -> Map.Map a b

getAToB (InjMap m n) = m

-- | get the part of direction b->a in the map

getBToA :: (Ord a, Ord b) => InjMap a b -> Map.Map b a

getBToA (InjMap m n) = n

-- | just for test :)

a :: InjMap Int String

a = empty