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Exact lookup

1. lookupOf :: forall k a (is :: IxList) s v . (Is k A_Fold, Eq a) => Optic' k is s (a, v) -> a -> s -> Maybe v

   optics-core	Optics.Fold

   The lookupOf function takes a Fold, 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 folded 2 [(2, 'a'), (4, 'b'), (4, 'c')]
   Just 'a'
   

2. lookupEntity :: String -> Maybe String

   tagsoup	Text.HTML.TagSoup.Entity

   Lookup an entity, using lookupNumericEntity if it starts with # and lookupNamedEntity otherwise

3. lookupNamedEntity :: String -> Maybe String

   tagsoup	Text.HTML.TagSoup.Entity

   Lookup a named entity, using htmlEntities

   lookupNamedEntity "amp" == Just "&"
   lookupNamedEntity "haskell" == Nothing
   

4. lookupNumericEntity :: String -> Maybe String

   tagsoup	Text.HTML.TagSoup.Entity

   Lookup a numeric entity, the leading '#' must have already been removed.

   lookupNumericEntity "65" == Just "A"
   lookupNumericEntity "x41" == Just "A"
   lookupNumericEntity "x4E" === Just "N"
   lookupNumericEntity "x4e" === Just "N"
   lookupNumericEntity "X4e" === Just "N"
   lookupNumericEntity "Haskell" == Nothing
   lookupNumericEntity "" == Nothing
   lookupNumericEntity "89439085908539082" == Nothing
   

5. lookupKey :: Key -> KeyMap v -> Maybe v

   autodocodec	Autodocodec.Aeson.Compat

   No documentation available.

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

   rio	RIO.HashMap

   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.

7. lookupGE :: Ord k => k -> Map k v -> Maybe (k, v)

   rio	RIO.Map

   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
   

8. lookupGT :: Ord k => k -> Map k v -> Maybe (k, v)

   rio	RIO.Map

   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
   

9. lookupIndex :: Ord k => k -> Map k a -> Maybe Int

   rio	RIO.Map

   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
   

10. lookupLE :: Ord k => k -> Map k v -> Maybe (k, v)

    rio	RIO.Map

    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')
    

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