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Lookup, find, or get find the value (if any) that is bound to a given key. The argument to this operation is the key, and the value is returned from the operation. If no value is found, some lookup functions raise an exception, while others return a default value (such as zero, null, or a specific value passed to the constructor).
The value of %phone-book{'John Doe'} is '555-1212'. The list of keys and values can be extracted using the built-in functions keys and values, respectively. So, for example, to print all the keys of a hash:
In computer programming, a collection is an abstract data type that is a grouping of items that can be used in a polymorphic way.. Often, the items are of the same data type such as int or string.
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 can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. A map implemented by a hash table is called a hash map.
The hash value in this case is derived from a hash function which takes a data input and returns a fixed length of bits. [ 2 ] Although hash algorithms, especially cryptographic hash algorithms, have been created with the intent of being collision resistant , they can still sometimes map different data to the same hash (by virtue of the ...
Keys are unique identifiers which map to particular values, which in turn can be anything from addresses, to documents, to arbitrary data. [2] Responsibility for maintaining the mapping from keys to values is distributed among the nodes, in such a way that a change in the set of participants causes a minimal amount of disruption.
Based on this non-growing implementation, a variety of different growing hash tables is given. These implementations allow for concurrent reads, inserts, updates (notably updating values based on the current value at the key) and removals (based upon updating using tombstones). Beyond that, variants on the basis of Intel TSX are provided. The ...
Computing the hash value of a given key x may be performed in constant time by computing g(x), looking up the second-level function associated with g(x), and applying this function to x. A modified version of this two-level scheme with a larger number of values at the top level can be used to construct a perfect hash function that maps S into a ...