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In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection.
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Aside from the seven "primitive" data types, every value in JavaScript is an object. [50] ECMAScript 2015 also added the Map data structure, which accepts arbitrary values as keys. [51] C++11 includes unordered_map in its standard library for storing keys and values of arbitrary types. [52] Go's built-in map implements a hash table in the form ...
In Haskell, the polymorphic function map :: (a -> b) -> [a] -> [b] is generalized to a polytypic function fmap :: Functor f => (a -> b) -> f a -> f b, which applies to any type belonging the Functor type class. The type constructor of lists [] can be defined as an instance of the Functor type class using the map function from the previous example:
However, since the code only uses methods common to the interface Map, a self-balancing binary tree could be used by calling the constructor of the TreeMap class (which implements the subinterface SortedMap), without changing the definition of the phoneBook variable, or the rest of the code, or using other underlying data structures that ...
For a more comprehensive listing of data structures, see List of data structures. The comparisons in this article are organized by abstract data type . As a single concrete data structure may be used to implement many abstract data types, some data structures may appear in multiple comparisons (for example, a hash map can be used to implement ...
A map, sometimes referred to as a dictionary, consists of a key/value pair. The key is used to order the sequence, and the value is somehow associated with that key. For example, a map might contain keys representing every unique word in a text and values representing the number of times that word appears in the text.
Large maps in Erlang use a persistent HAMT representation internally since release 18.0. [9] The Pony programming language uses a HAMT for the hash map in its persistent collections package. [10] The im and im-rc crates, which provide persistent collection types for the Rust programming language, use a HAMT for their persistent hash tables and ...