Type Theory
In type theory, sets are generally identified with their indicator function: accordingly, a set of values of type may be denoted by or . (Subtypes and subsets may be modeled by refinement types, and quotient sets may be replaced by setoids.) The characteristic function F of a set S is defined as: 
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.
Read more about this topic: Set (abstract Data Type)
Famous quotes containing the words type and/or theory:
“One type of rice nourishes one hundred types of people.”
—Chinese proverb.
“every subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that an objective, physical theory will abandon that point of view.”
—Thomas Nagel (b. 1938)