<
theory> The
discriminated union of two sets A and B is
A + B =
(inA, a) | a in A U
(inB, b)| b in B
where inA and inB are arbitrary tags which specify which
summand an element originates from.
A
type (especially an
algebraic data type) might be
described as a
discriminated union if it is a
sum type whose
objects consist of a tag to say which part of the
union they
belong to and a value of the corresponding type.
(1995-04-25)