Index set
In mathematics, an index set is a set whose members label members of another set. For instance, if the elements of a set A may be indexed or labeled by means of the elements of a set J, then J is an index set. The indexing consists of a surjective function from J onto A and the indexed collection is typically called an family, often written as j∈J.Examples
The set of all such indicator functions, , is an uncountable set indexed by.Other uses
In computational complexity theory and cryptography, an index set is a set for which there exists an algorithm that can sample the set efficiently; e.g., on input, can efficiently select a poly-bit long element from the set.
