On 12/02/2011 03:29 PM, 88888 Dihedral wrote:
I clear my point a hash is a collection of (key, value) pairs that have well defined methods and behavior to be used in programming. The basic operations of a hash normally includes the following: 1. insertion of a (key, value) pair into the hash 2. deletion of a (key, value) from the hash 3. inquiring a hash by a key to retrieve the value if the (key, value) pair available in the hash. If no key matched, the hash will return a not found result. The hash can grow with (k,v) pairs accumulated in the run time. An auto memory management mechanism is required for a hash of a non-fixed size of (k,v) pairs. Some implementations of a hash might pose some restrictions of k and v for some reasons. But in object programming k and v can be objects to be manipulated by the programmer.
Strictly speaking, what you're describing is just a dictionary/mapping abstract data type (ADT), not a hashtable. Hashtable is a particular way to implement the dictionary/mapping ADT. Python's dictionary is implemented as hashtable, but there are other ways to implement a dictionary/mapping, such as using a sorted tree.
For a data structure to be considered a Hashtable, in addition to having the properties of a dictionary that you described, the data structure must also uses a "hashing function" to encode the dictionary's keys into integer that will be used to calculate the index for the corresponding value in its internal array. A hashtable also must provide mechanism to deal with hash collisions to maintains its invariants as a dictionary.
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