lookup -fgl

lookup :: Eq a => a -> [(a, b)] -> Maybe b
base Prelude, base Data.List
lookup key assocs looks up a key in an association list.
lookup :: HashTable key val -> key -> IO (Maybe val)
base Data.HashTable
Looks up the value of a key in the hash table.
lookup :: Key -> IntMap a -> Maybe a
containers Data.IntMap.Strict, containers Data.IntMap.Lazy
O(min(n,W)). Lookup the value at a key in the map. See also lookup.
lookup :: Ord k => k -> Map k a -> Maybe a
containers Data.Map.Lazy, containers Data.Map.Strict
O(log n). Lookup the value at a key in the map. The function will return the corresponding value as (Just value), or Nothing if the key isn't in the map. An example of using lookup: > import Prelude hiding (lookup) > import Data.Map > > employeeDept = fromList([("John","Sales"), ("Bob","IT")]) > deptCountry = fromList([("IT","USA"), ("Sales","France")]) > countryCurrency = fromList([("USA", "Dollar"), ("France", "Euro")]) > > employeeCurrency :: String -> Maybe String > employeeCurrency name = do > dept <- lookup name employeeDept > country <- lookup dept deptCountry > lookup country countryCurrency > > main = do > putStrLn $ "John's currency: " ++ (show (employeeCurrency "John")) > putStrLn $ "Pete's currency: " ++ (show (employeeCurrency "Pete")) The output of this program: > John's currency: Just "Euro" > Pete's currency: Nothing
lookupGE :: Key -> IntMap a -> Maybe (Key, a)
containers Data.IntMap.Strict, containers Data.IntMap.Lazy
O(log n). Find smallest key greater or equal to the given one and return the corresponding (key, value) pair. > lookupGE 3 (fromList [(3,'a'), (5,'b')]) == Just (3, 'a') > lookupGE 4 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b') > lookupGE 6 (fromList [(3,'a'), (5,'b')]) == Nothing
lookupGE :: Key -> IntSet -> Maybe Key
containers Data.IntSet
O(log n). Find smallest element greater or equal to the given one. > lookupGE 3 (fromList [3, 5]) == Just 3 > lookupGE 4 (fromList [3, 5]) == Just 5 > lookupGE 6 (fromList [3, 5]) == Nothing
lookupGE :: Ord a => a -> Set a -> Maybe a
containers Data.Set
O(log n). Find smallest element greater or equal to the given one. > lookupGE 3 (fromList [3, 5]) == Just 3 > lookupGE 4 (fromList [3, 5]) == Just 5 > lookupGE 6 (fromList [3, 5]) == Nothing
lookupGE :: Ord k => k -> Map k v -> Maybe (k, v)
containers Data.Map.Lazy, containers Data.Map.Strict
O(log n). Find smallest key greater or equal to the given one and return the corresponding (key, value) pair. > lookupGE 3 (fromList [(3,'a'), (5,'b')]) == Just (3, 'a') > lookupGE 4 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b') > lookupGE 6 (fromList [(3,'a'), (5,'b')]) == Nothing
lookupGT :: Key -> IntMap a -> Maybe (Key, a)
containers Data.IntMap.Strict, containers Data.IntMap.Lazy
O(log n). Find smallest key greater than the given one and return the corresponding (key, value) pair. > lookupGT 4 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b') > lookupGT 5 (fromList [(3,'a'), (5,'b')]) == Nothing
lookupGT :: Key -> IntSet -> Maybe Key
containers Data.IntSet
O(log n). Find smallest element greater than the given one. > lookupGT 4 (fromList [3, 5]) == Just 5 > lookupGT 5 (fromList [3, 5]) == Nothing
lookupGT :: Ord a => a -> Set a -> Maybe a
containers Data.Set
O(log n). Find smallest element greater than the given one. > lookupGT 4 (fromList [3, 5]) == Just 5 > lookupGT 5 (fromList [3, 5]) == Nothing
lookupGT :: Ord k => k -> Map k v -> Maybe (k, v)
containers Data.Map.Lazy, containers Data.Map.Strict
O(log n). Find smallest key greater than the given one and return the corresponding (key, value) pair. > lookupGT 4 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b') > lookupGT 5 (fromList [(3,'a'), (5,'b')]) == Nothing
lookupHeader :: HeaderName -> [Header] -> Maybe String
HTTP Network.HTTP.Headers
lookupHeader hdr hdrs locates the first header matching hdr in the list hdrs.
lookupIndex :: Ord a => a -> Set a -> Maybe Int
containers Data.Set
O(log n). Lookup the index of an element, which is its zero-based index in the sorted sequence of elements. The index is a number from 0 up to, but not including, the size of the set. > isJust (lookupIndex 2 (fromList [5,3])) == False > fromJust (lookupIndex 3 (fromList [5,3])) == 0 > fromJust (lookupIndex 5 (fromList [5,3])) == 1 > isJust (lookupIndex 6 (fromList [5,3])) == False
lookupIndex :: Ord k => k -> Map k a -> Maybe Int
containers Data.Map.Lazy, containers Data.Map.Strict
O(log n). Lookup the index of a key, which is its zero-based index in the sequence sorted by keys. The index is a number from 0 up to, but not including, the size of the map. > isJust (lookupIndex 2 (fromList [(5,"a"), (3,"b")])) == False > fromJust (lookupIndex 3 (fromList [(5,"a"), (3,"b")])) == 0 > fromJust (lookupIndex 5 (fromList [(5,"a"), (3,"b")])) == 1 > isJust (lookupIndex 6 (fromList [(5,"a"), (3,"b")])) == False
lookupLE :: Key -> IntMap a -> Maybe (Key, a)
containers Data.IntMap.Strict, containers Data.IntMap.Lazy
O(log n). Find largest key smaller or equal to the given one and return the corresponding (key, value) pair. > lookupLE 2 (fromList [(3,'a'), (5,'b')]) == Nothing > lookupLE 4 (fromList [(3,'a'), (5,'b')]) == Just (3, 'a') > lookupLE 5 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b')
lookupLE :: Key -> IntSet -> Maybe Key
containers Data.IntSet
O(log n). Find largest element smaller or equal to the given one. > lookupLE 2 (fromList [3, 5]) == Nothing > lookupLE 4 (fromList [3, 5]) == Just 3 > lookupLE 5 (fromList [3, 5]) == Just 5
lookupLE :: Ord a => a -> Set a -> Maybe a
containers Data.Set
O(log n). Find largest element smaller or equal to the given one. > lookupLE 2 (fromList [3, 5]) == Nothing > lookupLE 4 (fromList [3, 5]) == Just 3 > lookupLE 5 (fromList [3, 5]) == Just 5
lookupLE :: Ord k => k -> Map k v -> Maybe (k, v)
containers Data.Map.Lazy, containers Data.Map.Strict
O(log n). Find largest key smaller or equal to the given one and return the corresponding (key, value) pair. > lookupLE 2 (fromList [(3,'a'), (5,'b')]) == Nothing > lookupLE 4 (fromList [(3,'a'), (5,'b')]) == Just (3, 'a') > lookupLE 5 (fromList [(3,'a'), (5,'b')]) == Just (5, 'b')
lookupLT :: Key -> IntMap a -> Maybe (Key, a)
containers Data.IntMap.Strict, containers Data.IntMap.Lazy
O(log n). Find largest key smaller than the given one and return the corresponding (key, value) pair. > lookupLT 3 (fromList [(3,'a'), (5,'b')]) == Nothing > lookupLT 4 (fromList [(3,'a'), (5,'b')]) == Just (3, 'a')

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