ListWrapper.Dict

A dictionary implementation using List. The keys can be any type includes recodes and custom type. This module provides all functions does Dict, except 'foldl', 'foldr', 'merge'.

Insert, remove, and query operations all take O(n) time. Only for a few elements.

To determine equality, use 'eq' instead of '(==)'.

Dictionaries

type Dict k v

A dictionary of keys and values.

Build

empty : Dict k v

Create an empty dictionary.

singleton : k -> v -> Dict k v

Create a dictionary with one key-value pair.

insert : k -> v -> Dict k v -> Dict k v

Insert a key-value pair into a dictionary. Replaces value when there is a collision.

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.

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.

Query

isEmpty : Dict k v -> Bool

Determine if a dictionary is empty.

member : k -> Dict k v -> Bool

Determine if a key is in a dictionary.

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

Get the value associated with a key.

size : Dict k v -> Int

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

eq : Dict k v -> Dict k v -> Bool

Determine if given two dictionary are the same.

Lists

keys : Dict k v -> List k

Get all of the keys in a dictionary. The order is not Fixed.

values : Dict k v -> List v

Get all of the values in a dictionary. The order is not Fixed.

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

Convert a dictionary into an association list of key-value pairs. The order is not Fixed.

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

Convert an association list into a dictionary. This function takes O(n^2) for n-element list.

Transform

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

Apply a function to all values in a dictionary.

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

Fold over the key-value pairs in a dictionary. The order is not fixed.

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

Keep only the key-value pairs that pass the given test.

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

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.

Combine

union : Dict k v -> Dict k v -> Dict k v

Combine two dictionaries. If there is a collision, preference is given to the first dictionary.

intersect : Dict k v -> Dict k v -> Dict k v

Keep a key-value pair when its key appears in the second dictionary. Preference is given to values in the first dictionary.

diff : Dict k a -> Dict k b -> Dict k a

Keep a key-value pair when its key does not appear in the second dictionary.

YuyaAizawa/list-wrapper/1.0.0