A dictionary data structure allowing for many-to-one, one-to-many and many-to-many relationships.
These, along with the ordinary Dict, give you all the relations you might need:
- one-to-one:
Dict - many-to-one:
BiDict - one-to-many:
MultiDict - many-to-many:
MultiBiDict
The many-to-* variants allow you to ask for the reverse mapping (from values to keys) - see the getReverse functions.
There are both a Dict-using and an assoc-list-using variant for each of these. Thus, one needs comparable keys and values and the other can hold any types, but has slightly worse performance characteristics.
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"]oneToMany : MultiDict String Int
oneToMany =
MultiDict.empty
|> MultiDict.insert "A" 1
|> MultiDict.insert "B" 2
|> MultiDict.insert "A" 3
|> MultiDict.insert "D" 4
MultiDict.get "A" oneToMany
--> Set.fromList [1, 3]manyToMany : MultiBiDict String Int
manyToMany =
MultiBiDict.empty
|> MultiBiDict.insert "A" 1
|> MultiBiDict.insert "B" 2
|> MultiBiDict.insert "C" 3
|> MultiBiDict.insert "A" 2
MultiBiDict.get "A" manyToMany
--> Set.fromList [1, 2]
MultiBiDict.getReverse 2 manyToMany
--> Set.fromList ["A", "B"]