A dictionary that maintains a mapping from the values back to keys, allowing for modelling many-to-one relationships.
Example usage:
manyToOne : BiDict String Int
manyToOne =
BiDict.empty
|> BiDict.insert "A" 1
|> BiDict.insert "B" 2
|> BiDict.insert "C" 1
|> BiDict.insert "D" 4
BiDict.getReverse 1 manyToOne
--> Set.fromList ["A", "C"]
The underlying data structure. Think about it as
type alias BiDict a b =
{ forward : Dict a b -- just a normal Dict!
, reverse : Dict b (Set a) -- the reverse mappings!
}
toDict : BiDict comparable1 comparable2 -> Dict comparable1 comparable2
Convert BiDict into a Dict. (Throw away the reverse mapping.)
fromDict : Dict comparable1 comparable2 -> BiDict comparable1 comparable2
Convert Dict into a BiDict. (Compute the reverse mapping.)
getReverse : comparable2 -> BiDict comparable1 comparable2 -> Set comparable1
Get the keys associated with a value. If the value is not found, return an empty set.
uniqueValues : BiDict comparable1 comparable2 -> List comparable2
Get a list of unique values in the dictionary.
uniqueValuesCount : BiDict comparable1 comparable2 -> Basics.Int
Get a count of unique values in the dictionary.
toReverseList : BiDict comparable1 comparable2 -> List ( comparable2, Set comparable1 )
Convert a dictionary into a reverse association list of value-keys pairs.
empty : BiDict comparable1 comparable2
Create an empty dictionary.
singleton : comparable1 -> comparable2 -> BiDict comparable1 comparable2
Create a dictionary with one key-value pair.
insert : comparable1 -> comparable2 -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Insert a key-value pair into a dictionary. Replaces value when there is a collision.
update : comparable1 -> (Maybe comparable2 -> Maybe comparable2) -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Update the value of a dictionary for a specific key with a given function.
remove : comparable1 -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Remove a key-value pair from a dictionary. If the key is not found, no changes are made.
isEmpty : BiDict comparable1 comparable2 -> Basics.Bool
Determine if a dictionary is empty.
isEmpty empty == True
member : comparable1 -> BiDict comparable1 comparable2 -> Basics.Bool
Determine if a key is in a dictionary.
get : comparable1 -> BiDict comparable1 comparable2 -> Maybe comparable2
Get the value associated with a key. If the key is not found, return
Nothing
. This is useful when you are not sure if a key will be in the
dictionary.
animals = fromList [ ("Tom", Cat), ("Jerry", Mouse) ]
get "Tom" animals == Just Cat
get "Jerry" animals == Just Mouse
get "Spike" animals == Nothing
size : BiDict comparable1 comparable2 -> Basics.Int
Determine the number of key-value pairs in the dictionary.
keys : BiDict comparable1 comparable2 -> List comparable1
Get all of the keys in a dictionary, sorted from lowest to highest.
keys (fromList [ ( 0, "Alice" ), ( 1, "Bob" ) ]) == [ 0, 1 ]
values : BiDict comparable1 comparable2 -> List comparable2
Get all of the values in a dictionary, in the order of their keys.
values (fromList [ ( 0, "Alice" ), ( 1, "Bob" ) ]) == [ "Alice", "Bob" ]
toList : BiDict comparable1 comparable2 -> List ( comparable1, comparable2 )
Convert a dictionary into an association list of key-value pairs, sorted by keys.
fromList : List ( comparable1, comparable2 ) -> BiDict comparable1 comparable2
Convert an association list into a dictionary.
map : (comparable1 -> comparable21 -> comparable22) -> BiDict comparable1 comparable21 -> BiDict comparable1 comparable22
Apply a function to all values in a dictionary.
foldl : (comparable1 -> comparable2 -> acc -> acc) -> acc -> BiDict comparable1 comparable2 -> acc
Fold over the key-value pairs in a dictionary from lowest key to highest key.
getAges users =
Dict.foldl addAge [] users
addAge _ user ages =
user.age :: ages
-- getAges users == [33,19,28]
foldr : (comparable1 -> comparable2 -> acc -> acc) -> acc -> BiDict comparable1 comparable2 -> acc
Fold over the key-value pairs in a dictionary from highest key to lowest key.
getAges users =
Dict.foldr addAge [] users
addAge _ user ages =
user.age :: ages
-- getAges users == [28,19,33]
filter : (comparable1 -> comparable2 -> Basics.Bool) -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Keep only the key-value pairs that pass the given test.
partition : (comparable1 -> comparable2 -> Basics.Bool) -> BiDict comparable1 comparable2 -> ( BiDict comparable1 comparable2, BiDict comparable1 comparable2 )
Partition a dictionary according to some test. The first dictionary contains all key-value pairs which passed the test, and the second contains the pairs that did not.
union : BiDict comparable1 comparable2 -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Combine two dictionaries. If there is a collision, preference is given to the first dictionary.
intersect : BiDict comparable1 comparable2 -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Keep a key-value pair when its key appears in the second dictionary. Preference is given to values in the first dictionary.
diff : BiDict comparable1 comparable2 -> BiDict comparable1 comparable2 -> BiDict comparable1 comparable2
Keep a key-value pair when its key does not appear in the second dictionary.
merge : (comparable1 -> comparable21 -> acc -> acc) -> (comparable1 -> comparable21 -> comparable22 -> acc -> acc) -> (comparable1 -> comparable22 -> acc -> acc) -> BiDict comparable1 comparable21 -> BiDict comparable1 comparable22 -> acc -> acc
The most general way of combining two dictionaries. You provide three accumulators for when a given key appears:
You then traverse all the keys from lowest to highest, building up whatever you want.