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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.
Therefore, compilers will attempt to transform the first form into the second; this type of optimization is known as map fusion and is the functional analog of loop fusion. [2] Map functions can be and often are defined in terms of a fold such as foldr, which means one can do a map-fold fusion: foldr f z . map g is equivalent to foldr (f .
As sets can be interpreted as a kind of map (by the indicator function), sets are commonly implemented in the same way as (partial) maps (associative arrays) – in this case in which the value of each key-value pair has the unit type or a sentinel value (like 1) – namely, a self-balancing binary search tree for sorted sets [definition needed ...
Go's built-in map implements a hash table in the form of a type. [53] Java programming language includes the HashSet, HashMap, LinkedHashSet, and LinkedHashMap generic collections. [54] Python's built-in dict implements a hash table in the form of a type. [55] Ruby's built-in Hash uses the open addressing model from Ruby 2.4 onwards. [56]
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.
More generally, a pairing function on a set is a function that maps each pair of elements from into an element of , such that any two pairs of elements of are associated with different elements of , [5] [a] or a bijection from to .
An entity–attribute–value model (EAV) is a data model optimized for the space-efficient storage of sparse—or ad-hoc—property or data values, intended for situations where runtime usage patterns are arbitrary, subject to user variation, or otherwise unforeseeable using a fixed design. The use-case targets applications which offer a large ...
That is, the pair (,) has the homotopy extension property if any map : (({}) ()) can be extended to a map ′: (i.e. and ′ agree on their common domain). If the pair has this property only for a certain codomain Y {\displaystyle Y\,\!} , we say that ( X , A ) {\displaystyle (X,A)\,\!} has the homotopy extension property with respect to Y ...