TypeRepMap is a heterogeneous data structure similar in its essence to Map with types as keys, where each value has the type of its key. In addition to that, each value is wrapped in an interpretation f.

Here is an example of using Maybe as an interpretation, with a comparison to Map:

 Map String (Maybe String)          TypeRepMap Maybe
---------------------------       ---------------------
 "Int"  -> Just "5"                 Int  -> Just 5
 "Bool" -> Just "True"              Bool -> Just True
 "Char" -> Nothing                  Char -> Nothing

The runtime representation of TypeRepMap is an array, not a tree. This makes lookup significantly more efficient.

A TypeRepMap with no values stored in it.

size empty == 0

member @a empty == False

Construct a TypeRepMap with a single element.

size (one x) == 1

member @a (one (x :: f a)) == True

Insert a value into a TypeRepMap. TypeRepMap optimizes for fast reads rather than inserts, as a trade-off inserts are O(n).

size (insert v tm) >= size tm

member @a (insert (x :: f a) tm) == True

Delete a value from a TypeRepMap.

TypeRepMap optimizes for fast reads rather than modifications, as a trade-off deletes are O(n), with an O(log(n)) optimization for when the element is already missing.

size (delete @a tm) <= size tm

member @a (delete @a tm) == False

>>> tm = delete @Bool $ insert (Just True) $ one (Just 'a')
>>> size tm
1
>>> member @Bool tm
False
>>> member @Char tm
True

Update a value at a specific key with the result of the provided function. When the key is not a member of the map, the original map is returned.

>>> trmap = fromList @(TypeRepMap Identity) [WrapTypeable $ Identity "a"]
>>> lookup @String $ adjust (fmap (++ "ww")) trmap
Just (Identity "aww")

Updates a value at a specific key, whether or not it exists. This can be used to insert, delete, or update a value of a given type in the map.

>>> func = (\case Nothing -> Just (Identity "new"); Just (Identity s) -> Just (Identity (reverse s)))
>>> lookup @String $ alter func empty
Just (Identity "new")
>>> trmap = fromList @(TypeRepMap Identity) [WrapTypeable $ Identity "helllo"]
>>> lookup @String $ alter func trmap
>>> Just (Identity "olleh")

Map over the elements of a TypeRepMap.

>>> tm = insert (Identity True) $ one (Identity 'a')
>>> lookup @Bool tm
Just (Identity True)
>>> lookup @Char tm
Just (Identity 'a')
>>> tm2 = hoist ((:[]) . runIdentity) tm
>>> lookup @Bool tm2
Just [True]
>>> lookup @Char tm2
Just "a"

The union of two TypeRepMaps using a combining function for conflicting entries. O(n + m)

The (left-biased) union of two TypeRepMaps in O(n + m). It prefers the first map when duplicate keys are encountered, i.e. union == unionWith const.

The intersection of two TypeRepMaps using a combining function

O(n + m)

The intersection of two TypeRepMaps. It keeps all values from the first map whose keys are present in the second.

O(n + m)

Lookup a value of the given type in a TypeRepMap.

>>> x = lookup $ insert (Identity (11 :: Int)) empty
>>> x :: Maybe (Identity Int)
Just (Identity 11)
>>> x :: Maybe (Identity ())
Nothing

Check if a value of the given type is present in a TypeRepMap.

>>> member @Char $ one (Identity 'a')
True
>>> member @Bool $ one (Identity 'a')
False

Get the amount of elements in a TypeRepMap.

Return the list of SomeTypeRep from the keys.

Return the list of keys by wrapping them with a user-provided function.

Return the list of key-value pairs by wrapping them with a user-provided function.

Existential wrapper around Typeable indexed by f type parameter. Useful for TypeRepMap structure creation form list of WrapTypeables.