Every structure has an associated an object called a structure
type (sometimes abbreviated stype, pronounced ``ess type'').
Structure types are created by the procedure MAKE-STYPE (see below)
and by the special form DEFINE-STRUCTURE-TYPE
Given a structure type S, one can access several things of interest:
- Constructor
- a procedure that will create uninitialized structures of
type S (e.g., the structure for a particular employee).
- Predicator
- a procedure (a type predicate) that returns true if its
argument is a structure of type S.
- Component selectors
- procedures that access the various components of
structures of type S (one selector per component).
- Handler
- the mechanism for specifying how a set of generic operations
will behave when applied to structures of type S.