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Within LTS Haskell 24.26 (ghc-9.10.3)

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Exact lookup

1. lookupKey :: Hashable k => k -> HashMap k v -> Maybe k

   unordered-containers	Data.HashMap.Internal.Strict

   For a given key, return the equal key stored in the map, if present, otherwise return Nothing. This function can be used for interning, i.e. to reduce memory usage.

2. lookupDefault :: Hashable k => v -> k -> HashMap k v -> v

   unordered-containers	Data.HashMap.Lazy

   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.

3. lookupKey :: Hashable k => k -> HashMap k v -> Maybe k

   unordered-containers	Data.HashMap.Lazy

   For a given key, return the equal key stored in the map, if present, otherwise return Nothing. This function can be used for interning, i.e. to reduce memory usage.

4. lookupDefault :: 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.

5. lookupKey :: Hashable k => k -> HashMap k v -> Maybe k

   unordered-containers	Data.HashMap.Strict

   For a given key, return the equal key stored in the map, if present, otherwise return Nothing. This function can be used for interning, i.e. to reduce memory usage.

6. lookupElement :: Hashable a => a -> HashSet a -> Maybe a

   unordered-containers	Data.HashSet

   For a given value, return the equal element in the set if present, otherwise return Nothing. This is useful for interning, i.e. to reduce memory usage.

7. lookupElement :: Hashable a => a -> HashSet a -> Maybe a

   unordered-containers	Data.HashSet.Internal

   For a given value, return the equal element in the set if present, otherwise return Nothing. This is useful for interning, i.e. to reduce memory usage.

8. 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
   

9. 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
   

10. 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
    

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