{- |

Module : $Header$

Description : Utils extending Data.List

Copyright : (c) Immanuel Normann, Uni Bremen 2007

License : GPLv2 or higher, see LICENSE.txt

Maintainer : inormann@jacobs-university.de

Stability : provisional

Portability : portable

-}

module Search.Utils.List where

import Data.List

filterMap :: (t -> Bool) -> (t -> a) -> [t] -> [a]

filterMap test fun lst = filterMap' lst []

where filterMap' [] acc = reverse acc

filterMap' (h:t) acc = filterMap' t acc'

where acc' = if test h then (fun h):acc else acc

{-

*Utils.List> filterMap even (*3) [1,2,3,4,5]

[6,12]

-}

updateListAndGetIndex :: (Eq a) => a -> [a] -> ([a], Int)

updateListAndGetIndex x table =

case (findIndex (== x) table)

of Nothing -> (table ++ [x], length table)

Just i -> (table, i)

filterIndecesAndElems :: (a -> Bool) -> [a] -> [(a,Int)]

filterIndecesAndElems p lst = getByIndices indices tmpLst -- das geht effizienter mit einem einzigen Listendruchlauf

where tmpLst = zip lst [0..((length lst) - 1)]

indices = findIndices p lst

{-

*Utils.List> filterIndecesAndElems even [1,2,3,4]

[(2,1),(4,3)]

*Utils.List> filterIndecesAndElems even [1,2,3,4,2]

[(2,1),(4,3),(2,4)]

-}

lookUpFirstEntry :: (Eq s) => s -> [s] -> Maybe Int

lookUpFirstEntry s ss =

case filterIndecesAndElems (s==) ss

of ((_,n):_) -> Just n

_ -> Nothing

{-

> lookUpFirstEntry 3 [1,2,3,4,5,4,3,2,1]

Just 2

-}

getByIndices :: [Int] -> [a] -> [a]

getByIndices indices lst = map (lst!!) admissbleIndices

where admissbleIndices = filter (\x -> (x>=0) && (x<(length lst))) indices

{-

*Utils.List> getByIndices [1,3] ["a","b","c","d"]

["b","d"]

*Utils.List> getByIndices [3,1] ["a","b","c","d"]

["d","b"]

*Utils.List> getByIndices [1,5] ["a","b","c","d"]

["b"]

*Utils.List> getByIndices [3,1,5,2] ["a","b","c","d"]

["d","b","c"]

*Utils.List> getByIndices [] ["a","b","c","d"]

[]

*Utils.List> getByIndices [-1] ["a","b","c","d"]

[]

-}

mapAssoc :: [(Int,Int)] -> [a] -> [(a,a)]

mapAssoc intPair lst = tmpMap (length lst) intPair lst

where tmpMap _ [] _ = []

tmpMap len ((m,n):rest) lst =

if 0 <= m && 0 <= n && m < len && n < len

then (lst!!m,lst!!n):(tmpMap len rest lst)

else (tmpMap len rest lst)

{-

*Utils.List> mapAssoc [(1,3),(2,1)] ["a","b","c","d"]

[("b","d"),("c","b")]

*Utils.List> mapAssoc [(1,-3),(2,1)] ["a","b","c","d"]

[("c","b")]

*Utils.List> mapAssoc [(1,999),(2,1)] ["a","b","c","d"]

[("c","b")]

-}

listsToSortedIndices :: (Eq a) => [a] -> [a] -> [Int]

listsToSortedIndices as bs = findIndices (\x -> elem x as) bs -- geht natuerlich effizienter

{- indices werden in aufsteigender Reihenfolge ausgeben

*Utils.List> listToSortedIndices [2,4] [1,2,3,4,5]

[1,3]

*Utils.List> listToSortedIndices [2,4] [4,2,3,4,5]

[0,1,3]

*Utils.List> listToSortedIndices [0,2,4] [1,2]

[1]

-}

listsToFirstIndices :: (Eq a) => [a] -> [a] -> [Int]

listsToFirstIndices = (accIndices [] 0)

where accIndices acc k [] _ = acc

accIndices acc k (a:as) bs =

case (elemIndex a bs)

of Just k -> accIndices (k:acc) k as bs

Nothing -> accIndices acc (k+1) as bs

makeRightUnique :: (Eq a) => [(a,a)] -> [(a,a)]

makeRightUnique lst = nubBy fstEq lst

where fstEq (a,_) (b,_) = a == b

{-

*Utils.List> makeRightUnique [(1,3),(2,4),(1,2)]

[(1,3),(2,4)]

-}

isRightUnique :: (Eq a) => [(a,a)] -> Bool

isRightUnique lst = (length lst') == (length $ makeRightUnique lst')

where lst' = nub lst

{-

*Utils.List> isRightUnique [(1,3),(2,4),(1,2)]

False

*Utils.List> isRightUnique [(1,3),(2,4),(1,3)]

True

-}

filterNeq lst = filter unequalPair lst

where unequalPair (x,y) = x /= y

--removeIdentities :: (Eq a) => [(a,a)] -> [(a,a)]

--removeIdentities = filter (\(x,y) -> not (x == y))

mapShow :: (Show a) => String -> [a] -> [Char]

mapShow _ [] = ""

mapShow _ [x] = show x

mapShow sep (h:r) = show h ++ sep ++ (mapShow sep r)

-- mapShow kann man bestimmt eleganter schreiben. s. Show class

pprintList [] = putStrLn ""

pprintList (h:t) = putStrLn (show h) >> pprintList t