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11 The Built-In Classes

Overview

This chapter contains an entry for every class defined by Dylan.

The superclasses listed for a class C are those classes defined by the Dylan language from which C most directly inherits. They are not required to be the direct superclasses of C, because implementations are free to insert implementation-defined classes in the class hierarchy. However, any classes defined by Dylan that appear in the class precedence list of C must appear in the same order in which they would appear if the specified superclasses were the direct superclasses of C, in the order given.

All classes are specified as open or sealed. A class may be specifed as abstract; if it is not, then it is concrete. A class may be specified as primary; if it is not, than it is free. A class may be specified as instantiable. If it is not, then it is uninstantiable. Chapter 9, "Sealing," contains a complete description of these characteristics.

An implementation may choose to impose fewer restrictions than specified. For example, a class specified as sealed may be left open, and a class specified as primary may be left free. However, any program that takes advantage of this liberality will not be portable.

Each class entry includes tables of operations defined on the class. These tables are cross references to Chapter 12, "The Built-In Functions," and represent redundant information. A function, generic function, or method is listed under a class if one of its arguments is specialized on the class. In addition, constructors are listed. Not all generic functions that specialize on <object> are listed.