Definition of A "type"
(Parnas, Shore & Weiss 1976) identified five definitions of a "type" that were used—sometimes implicitly—in the literature:
- Syntactic
- A type is a purely syntactic label associated with a variable when it is declared. Such definitions of "type" do not give any semantic meaning to types.
- Representation
- A type is defined in terms of its composition of more primitive types—often machine types.
- Representation and behaviour
- A type is defined as its representation and a set of operators manipulating these representations.
- Value space
- A type is a set of possible values which a variable can posses. Such definitions make it possible to speak about (disjoint) unions or Cartesian products of types.
- Value space and behaviour
- A type is a set of values which a variable can posses and a set of functions that one can apply to these values.
The definition in terms of a representation was often done in imperative languages such as ALGOL and Pascal, while the definition in terms of a value space and behaviour was used in higher-level languages such as Simula and CLU.
Read more about this topic: Data Type
Famous quotes containing the words definition of a, definition of, definition and/or type:
“... we all know the wag’s definition of a philanthropist: a man whose charity increases directly as the square of the distance.”
—George Eliot [Mary Ann (or Marian)
“Although there is no universal agreement as to a definition of life, its biological manifestations are generally considered to be organization, metabolism, growth, irritability, adaptation, and reproduction.”
—The Columbia Encyclopedia, Fifth Edition, the first sentence of the article on “life” (based on wording in the First Edition, 1935)
“One definition of man is “an intelligence served by organs.””
—Ralph Waldo Emerson (1803–1882)
“Only that type of story deserves to be called moral that shows us that one has the power within oneself to act, out of the conviction that there is something better, even against one’s own inclination.”
—Johann Wolfgang Von Goethe (1749–1832)