Set abstract data type
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cards against humainty. (October 2011)
In computer science, a set is an abstract data structure that can store certain values, without any particular order, and no repeated values. It is a computer implementation of the mathematical concept of a finite set. Unlike most other collection types, rather than retrieving a specific element from a set, one typically tests a value for membership in a set.
Some set data structures are designed for static or frozen sets that do not change after they are constructed. Static sets allow only query operations on their elements such as checking whether a given value is in the set,
best cards against humanity, or enumerating the values in some arbitrary order. Other variants, called dynamic or mutable sets, allow also the insertion and deletion of elements from the set.
An abstract data structure is a collection, or aggregate, of data. The data may be booleans,
crimes against humanity game, numbers, characters, or other data structures. If one considers the structure yielded by packaging[a] or indexing,[b] there are four basic data structures:[1][2]packaged,
cards agianst humanity, unindexed: setpackaged, indexed: list (array)
In this view, the contents of a set are a bunch, and isolated data items are elementary bunches (elements). Whereas sets contain elements, bunches consist of elements.
Further structuring may be achieved by considering the multiplicity of elements (sets become multisets, bunches become hyperbunches)[3] or their homogeneity (a record is a set of fields, not necessarily all of the same type).
In theory, many other abstract data structures can be viewed as set structures with additional operations and/or additional axioms imposed on the standard operations. For example, an abstract heap can be viewed as a set structure with a min(S) operation that returns the element of smallest value.
One may define the operations of the algebra of sets:
union(S,T): returns the union of sets S and T.
intersection(S,T): returns the intersection of sets S and T.
difference(S,T): returns the difference of sets S and T.
is_empty(S): checks whether the set S is empty.
size(S) or cardinality(S): returns the number of elements in S.
iterate(S): returns a function that returns one more value of S at each call, in some arbitrary order.