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Exact lookup

1. lookup :: Ord k => k -> SetMap k a -> Set a

   multimap	Data.SetMap

   O(log n). Lookup the value at a key in the map. The function will return the corrsponding values as a List, or the empty list if no values are associated witht the given key.

2. lookup :: Key -> NEIntMap a -> Maybe a

   nonempty-containers	Data.IntMap.NonEmpty

   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.NonEmpty
   
   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
   

3. lookup :: Ord k => k -> NEMap k a -> Maybe a

   nonempty-containers	Data.Map.NonEmpty

   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.NonEmpty
   
   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
   

4. lookup :: Int -> NESeq a -> Maybe a

   nonempty-containers	Data.Sequence.NonEmpty

   The element at the specified position, counting from 0. If the specified position is negative or at least the length of the sequence, lookup returns Nothing. Unlike index, this can be used to retrieve an element without forcing it.

5. lookup :: Eq a => a -> [(a, b)] -> Maybe b

   prelude-compat	Data.List2010

   No documentation available.

6. lookup :: Eq a => a -> [(a, b)] -> Maybe b

   prelude-compat	Prelude2010

   No documentation available.

7. lookup :: Resolver -> Domain -> TYPE -> IO (Either DNSError [RData])

   dns	Network.DNS.LookupRaw

   Look up resource records of a specified type for a domain, collecting the results from the ANSWER section of the response. See the documentation of lookupRaw to understand the concrete behavior. Cache is used if resolvCache is Just. Example:

   >>> rs <- makeResolvSeed defaultResolvConf
   
   >>> withResolver rs $ \resolver -> lookup resolver "www.example.com" A
   Right [93.184.216.34]
   

8. lookup :: FieldName -> Data -> FieldName -> LookupFields -> BuildTransformSpecs

   hvega	Graphics.Vega.VegaLite

   Perform a lookup of named fields between two data sources. This allows you to find values in one data source based on the values in another (like a relational join). Use lookupSelection for linking data with interactive selections. See the Vega-Lite documentation for further details. The following would return the values in the age and height fields from lookup_people.csv for all rows where the value in the name column in that file matches the value of person in the primary data source.

   peopleData = dataFromUrl "data/lookup_people.csv" []
   lfields = LuFields ["age", "height"]
   trans = transform
   . lookup "person" peopleData "name" lfields
   

   Note that the interface has changed in version 0.5.0.0: the output field names argument now uses the new LookupFields type. This provides greater flexibility in naming and default behaviour. The conversion from version 0.4 is simple: change

   lookup key1 dataSource key2 fields
   

   to

   lookup key1 dataSource key2 (LuFields fields)
   

9. lookup :: Eq a => a -> [(a, b)] -> Maybe b

   mixed-types-num	Numeric.MixedTypes.PreludeHiding

   lookup key assocs looks up a key in an association list. For the result to be Nothing, the list must be finite.

   Examples

   >>> lookup 2 []
   Nothing
   

   >>> lookup 2 [(1, "first")]
   Nothing
   

   >>> lookup 2 [(1, "first"), (2, "second"), (3, "third")]
   Just "second"
   

10. lookup :: Hashable key => key -> Map key value -> STM (Maybe value)

    stm-containers	StmContainers.Map

    Look up an item.

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