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add a new (,) pair to the collection, mapping the key to its new value. Any existing mapping is overwritten. The arguments to this operation are the key and the value. Remove or delete remove a (,) pair from the collection, unmapping a given key from its value. The argument to this operation is the key.
In C++, the std::map class is templated which allows the data types of keys and values to be different for different map instances. For a given instance of the map class the keys must be of the same base type. The same must be true for all of the values.
In computing, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [2] A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value ...
One might desire to have a LinkedList of int, but this is not directly possible. Instead Java defines primitive wrapper classes corresponding to each primitive type: Integer and int, Character and char, Float and float, etc. One can then define a LinkedList using the boxed type Integer and insert int values into the list by boxing them as ...
In C++, the Standard Template Library (STL) provides the set template class, which is typically implemented using a binary search tree (e.g. red–black tree); SGI's STL also provides the hash_set template class, which implements a set using a hash table. C++11 has support for the unordered_set template class, which is implemented using a hash ...
Example of a web form with name-value pairs. A name–value pair, also called an attribute–value pair, key–value pair, or field–value pair, is a fundamental data representation in computing systems and applications. Designers often desire an open-ended data structure that allows for future extension without modifying existing code or data.
If a trait requires the consuming class to provide certain methods, the trait cannot know if those methods are semantically equivalent to the trait's needs. For some dynamic languages, such as Perl, the required method can only be identified by a method name, not a full method signature, making it harder to guarantee that the required method is appropriate.
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: