Sort.Dict

A dictionary mapping unique keys to values.

Insert, remove, and query operations all take O(log n) time.

This implementation is based on Skinney/elm-dict-exploration, except that it uses Sorter instead of comparable, so it permits keys that are not comparable.

Dictionaries

type alias Dict key value =

Dict key value

A dictionary of keys and values. So a (Dict String User) is a dictionary that lets you look up a String (such as user names) and find the associated User.

Build

empty : Sorter k -> Dict k v

Create an empty dictionary.

singleton : Sorter k -> k -> v -> Dict k v

Create a dictionary with one key-value pair.

store : k -> v -> Dict k v -> Dict k v

Store a key-value pair in a dictionary. Replaces value when that key is already present.

remove : k -> Dict k v -> Dict k v

Remove a key-value pair from a dictionary. If the key is not found, no changes are made.

update : k -> (Maybe v -> Maybe v) -> Dict k v -> Dict k v

Update the value of a dictionary for a specific key with a given function. The given function gets the current value as a parameter and its return value determines if the value is updated or removed. New key-value pairs can be stored too.

Query

isEmpty : Dict k v -> Bool

Determine if a dictionary is empty. isEmpty empty == True

size : Dict k v -> Int

Determine the number of key-value pairs in the dictionary.

get : k -> Dict k v -> Maybe v

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

member : k -> Dict k v -> Bool

Determine if a key is in a dictionary.

Transform

map : (k -> a -> b) -> Dict k a -> Dict k b

Apply a function to all values in a dictionary.

filter : (k -> v -> Bool) -> Dict k v -> Dict k v

Keep a key-value pair when it satisfies a predicate.

foldl : (k -> v -> b -> b) -> b -> Dict k v -> b

Fold over the key-value pairs in a dictionary, in order from lowest key to highest key.

foldr : (k -> v -> b -> b) -> b -> Dict k v -> b

Fold over the key-value pairs in a dictionary, in order from highest key to lowest key.

partition : (k -> v -> Bool) -> Dict k v -> ( Dict k v, Dict k v )

Partition a dictionary according to a predicate. The first dictionary contains all key-value pairs which satisfy the predicate, and the second contains the rest.

Combine

storeAll :

{ from : Dict k v

, into : Dict k v

}

-> Dict k v

Take all the key-value pairs in the from dictionary and store them into the into dictionary.

intersect :

{ preferred : Dict k v

, other : Dict k v

}

-> Dict k v

Keep a key-value pair when its key appears in the both the preferred and in the other dictionary.

Preference for values and Sorter is given to values in the preferred dictionary.

diff :

{ original : Dict k v

, other : Dict k v

}

-> Dict k v

Keep a key-value pair when its key appears in the original dictionary but not in the other dictionary.

The original dictionary's Sorter will be used.

merge :

Sorter k

-> (k -> a -> result -> result)

-> (k -> a -> b -> result -> result)

-> (k -> b -> result -> result)

-> Dict k a

-> Dict k b

-> result

The most general way of combining two dictionaries. You provide three accumulators for when a given key appears:

Only in the left dictionary.
In both dictionaries.
Only in the right dictionary. You then traverse all the keys from lowest to highest, building up whatever you want.

Lists

keys : Dict k v -> List k

Get all of the keys in a dictionary, sorted from lowest to highest. keys (fromList [(0,"Alice"),(1,"Bob")]) == [0,1]

values : Dict k v -> List v

Get all of the values in a dictionary, in the order of their keys. values (fromList [(0,"Alice"),(1,"Bob")]) == ["Alice", "Bob"]

toList : Dict k v -> List ( k, v )

Convert a dictionary into an association list of key-value pairs, sorted by keys.

fromList : Sorter k -> List ( k, v ) -> Dict k v

Convert an association list into a dictionary.

rtfeldman/elm-sorter-experiment/1.0.0

Sort.Dict

Dictionaries

Build

Query

Transform

Combine

Lists

Modules