Opaque-type variables hold data retrieved
from opaque data types. Distinct-type variables hold
data retrieved from distinct data types. If you define a variable
with an opaque data type or a distinct data type, the variable can
only hold data of that type.
If you define an opaque data type
named point and a distinct data type named centerpoint,
you can define SPL variables to hold data from the two types, as the
following figure shows. Figure 1. Defining SPL variables to hold opaque and
distinct data types.
DEFINE a point;
DEFINE b centerpoint;
The variable a can only hold data of type point,
and b can only hold data of type centerpoint.