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Exact lookup

1. lookupDefault :: (Eq k, Hashable k) => v -> k -> HashMap k v -> v

   unordered-containers	Data.HashMap.Strict

   Return the value to which the specified key is mapped, or the default value if this map contains no mapping for the key. DEPRECATED: lookupDefault is deprecated as of version 0.2.11, replaced by findWithDefault.

2. lookupOf :: Eq k => Getting (Endo (Maybe v)) s (k, v) -> k -> s -> Maybe v

   lens	Control.Lens.Combinators

   The lookupOf function takes a Fold (or Getter, Traversal, Lens, Iso, etc.), a key, and a structure containing key/value pairs. It returns the first value corresponding to the given key. This function generalizes lookup to work on an arbitrary Fold instead of lists.

   >>> lookupOf folded 4 [(2, 'a'), (4, 'b'), (4, 'c')]
   Just 'b'
   

   >>> lookupOf each 2 [(2, 'a'), (4, 'b'), (4, 'c')]
   Just 'a'
   

   lookupOf :: Eq k => Fold s (k,v) -> k -> s -> Maybe v
   

3. lookupOf :: Eq k => Getting (Endo (Maybe v)) s (k, v) -> k -> s -> Maybe v

   lens	Control.Lens.Fold

   The lookupOf function takes a Fold (or Getter, Traversal, Lens, Iso, etc.), a key, and a structure containing key/value pairs. It returns the first value corresponding to the given key. This function generalizes lookup to work on an arbitrary Fold instead of lists.

   >>> lookupOf folded 4 [(2, 'a'), (4, 'b'), (4, 'c')]
   Just 'b'
   

   >>> lookupOf each 2 [(2, 'a'), (4, 'b'), (4, 'c')]
   Just 'a'
   

   lookupOf :: Eq k => Fold s (k,v) -> k -> s -> Maybe v
   

4. lookupCmsg :: CmsgId -> [Cmsg] -> Maybe Cmsg

   network	Network.Socket

   Locate a control message of the given type in a list of control messages. The following shows an example usage:

   (lookupCmsg CmsgIdIPv4TOS cmsgs >>= decodeCmsg) :: Maybe IPv4TOS
   

5. lookupResponseHeader :: forall (h :: Symbol) a (headers :: [Type]) r . HasResponseHeader h a headers => Headers headers r -> ResponseHeader h a

   gogol-core	Gogol.Prelude

   Look up a specific ResponseHeader, without having to know what position it is in the HList.

   >>> let example1 = addHeader 5 "hi" :: Headers '[Header "someheader" Int] String
   
   >>> let example2 = addHeader True example1 :: Headers '[Header "1st" Bool, Header "someheader" Int] String
   
   >>> lookupResponseHeader example2 :: ResponseHeader "someheader" Int
   Header 5
   

   >>> lookupResponseHeader example2 :: ResponseHeader "1st" Bool
   Header True
   

   Usage of this function relies on an explicit type annotation of the header to be looked up. This can be done with type annotations on the result, or with an explicit type application. In this example, the type of header value is determined by the type-inference, we only specify the name of the header:

   >>> :set -XTypeApplications
   
   >>> case lookupResponseHeader @"1st" example2 of { Header b -> b ; _ -> False }
   True
   

6. lookupEnv :: MonadIO m => String -> m (Maybe String)

   unliftio	UnliftIO.Environment

   Lifted lookupEnv.

7. lookupJust :: (Eq a, Partial) => a -> [(a, b)] -> b

   safe	Safe

   lookupJust key = fromJust . lookup key
   

8. lookupJustDef :: Eq a => b -> a -> [(a, b)] -> b

   safe	Safe

   No documentation available.

9. lookupJustNote :: (Partial, Eq a) => String -> a -> [(a, b)] -> b

   safe	Safe

   No documentation available.

10. lookupEnv :: String -> IO (Maybe String)

    base-compat	System.Environment.Compat

    Return the value of the environment variable var, or Nothing if there is no such value. For POSIX users, this is equivalent to getEnv.

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