* Primitive Procedures::
* Continuations::
* Application Hooks::
-* Generic Dispatch::
@end menu
@node Procedure Operations, Arity, Procedures, Procedures
there are @var{object}s.
@end deffn
-@node Application Hooks, Generic Dispatch, Continuations, Procedures
+@node Application Hooks, , Continuations, Procedures
@section Application Hooks
@cindex application hook (defn)
Changes the extra component of @var{entity} to be @var{object}. Returns
an unspecified value.
@end deffn
-
-@node Generic Dispatch, , Application Hooks, Procedures
-@section Generic Dispatch
-
-@cindex generic procedure
-@cindex procedure, generic
-MIT/GNU Scheme provides a generic dispatch mechanism that can choose
-an action to take based on the types of a set of objects. Performance
-is guaranteed by the use of a hash-based method cache.
-
-This is @emph{not} an object-oriented programming system, although it
-can provide the basis for such systems. The difference is that the
-generic dispatch doesn't have any model for the relationship between
-object types. Instead, there is a flat space of types and methods are
-selected by procedural examination of the given operand types.
-
-@menu
-* Generic Procedures::
-* Method Generators::
-* Dispatch Tags::
-@end menu
-
-@node Generic Procedures, Method Generators, Generic Dispatch, Generic Dispatch
-@subsection Generic Procedures
-
-@cindex method, of generic procedure
-The core of the dispatch mechanism is the @dfn{generic procedure}.
-This is a procedure that is called in the usual way, but which
-dispatches to a particular @dfn{method} based on the types of its
-arguments.
-
-@deffn procedure make-generic-procedure arity [name]
-Returns a new generic procedure accepting @var{arity}. @var{Arity}
-must specify a minimum of one argument.
-
-@var{Name} is used for debugging: it is a symbol that has no role in
-the semantics of the generic procedure. @var{Name} may be @code{#f}
-to indicate that the generic procedure is anonymous. If @var{name} is
-not specified, it defaults to @samp{#f}.
-
-Examples:
-
-@lisp
-(define foo-bar (make-generic-procedure 2 'bar))
-
-(define foo-baz (make-generic-procedure '(1 . 2) 'foo-baz))
-
-(define foo-mum (make-generic-procedure '(1 . #f)))
-@end lisp
-@end deffn
-
-@deffn procedure generic-procedure? object
-Returns @samp{#t} if @var{object} is a generic procedure,
-and @samp{#f} otherwise.
-@end deffn
-
-@deffn procedure generic-procedure-arity generic
-Returns the arity of @var{generic}, as given to
-@code{make-generic-procedure}.
-@end deffn
-
-@deffn procedure generic-procedure-name generic
-Returns the name of @var{generic}, as given to
-@code{make-generic-procedure}.
-@end deffn
-
-@deffn procedure generic-procedure-applicable? generic operands
-Returns @samp{#t} if @var{generic} is applicable to @var{operands}
-(which must be a list of objects), and @samp{#f} otherwise.
-@end deffn
-
-@deffn {condition type} condition-type:no-applicable-methods operator operands
-This condition type is signalled when a generic procedure is applied
-and there are no applicable methods for the given operands. The condition's
-@var{operator} field contains the generic procedure and the
-@var{operands} field contains the given operands.
-@end deffn
-
-@deffn {condition type} condition-type:extra-applicable-methods operator operands
-This condition type is signalled when a generic procedure is applied
-and there are more than one applicable methods for the given operands.
-The condition's @var{operator} field contains the generic procedure
-and the @var{operands} field contains the given operands.
-@end deffn
-
-@node Method Generators, Dispatch Tags, Generic Procedures, Generic Dispatch
-@subsection Method Generators
-
-Generic-procedure methods are dynamically chosen by @dfn{generators},
-which are procedures of two arguments. Each generic procedure has a
-set of associated generators. Whenever the procedure is applied, each
-associated generator is applied to two arguments: the generic
-procedure and a list of the dispatch tags for the operands. The
-return value from the generator is either a @dfn{method} (a procedure
-accepting that number of arguments) or @samp{#f}. In order for the
-application to succeed, exactly one of the generic procedure's
-generators must return a method.
-
-Once a method has been chosen, it is cached. A subsequent call to the
-generic procedure with operands of the same types will reuse that
-cached method. Consequently, it is important that generators be
-@dfn{functional}: they must always compute the same value from the
-same arguments.
-
-@deffn procedure add-generic-procedure-generator generic generator
-Adds @var{generator} to @var{generic}'s set of generators and returns
-an unspecified value.
-@end deffn
-
-@deffn procedure remove-generic-procedure-generator generic generator
-Removes @var{generator} from @var{generic}'s set of generators and
-returns an unspecified value.
-@end deffn
-
-@deffn procedure remove-generic-procedure-generators generic tags
-Calls each of @var{generic}'s set of generators on @var{tags} and
-removes each generator that returns a method. Returns an unspecified
-value.
-@end deffn
-
-@deffn procedure generic-procedure-generator-list generic
-Returns a list of @var{generic}'s generators.
-@end deffn
-
-As a convenience, each generic procedure can have a @dfn{default
-generator}, which is called only when all of the other generators have
-returned @samp{#f}. When created, a generic procedure has no default
-generator.
-
-@deffn procedure generic-procedure-default-generator generic
-Returns @var{generic}'s default generator.
-@end deffn
-
-@deffn procedure set-generic-procedure-default-generator! generic generator
-Sets @var{generic}'s default generator to @var{generator} and returns
-an unspecified value.
-@end deffn
-
-@node Dispatch Tags, , Method Generators, Generic Dispatch
-@subsection Dispatch Tags
-
-@cindex dispatch tag
-@cindex tag, dispatch
-A dispatch tag is an object that represents the ``type'' of an
-object, for the purposes of generic dispatch. Every object has an
-associated dispatch tag. Built-in objects like pairs or booleans have
-predefined tags, while dynamically typed objects like records have
-tags that are created as needed.
-
-@deffn procedure dispatch-tag object
-Returns the dispatch tag for @var{object}.
-
-@example
-@group
-(dispatch-tag #f) @result{} #[dispatch-tag 17 (boolean)]
-(dispatch-tag #t) @result{} #[dispatch-tag 17 (boolean)]
-(dispatch-tag (list)) @result{} #[dispatch-tag 18 (null)]
-(dispatch-tag (list 3)) @result{} #[dispatch-tag 19 (pair list)]
-@end group
-@end example
-@end deffn
-
-@deffn procedure built-in-dispatch-tag name
-Returns the built-in dispatch tag called @var{name}. @var{Name} must
-be a symbol that is the name of a known built-in dispatch tag.
-
-@example
-@group
-(built-in-dispatch-tag 'boolean) @result{} #[dispatch-tag 17 (boolean)]
-(built-in-dispatch-tag 'null) @result{} #[dispatch-tag 18 (null)]
-(built-in-dispatch-tag 'pair) @result{} #[dispatch-tag 19 (pair list)]
-(built-in-dispatch-tag 'list) @result{} #[dispatch-tag 19 (pair list)]
-@end group
-@end example
-@end deffn
-
-@deffn procedure built-in-dispatch-tags
-Returns a list of the built-in dispatch tags.
-@end deffn
-
-@deffn procedure record-type-dispatch-tag record-type
-Returns the dispatch tag associate with @var{record-type}. See
-@xref{Records}, for more information about record types.
-@end deffn
-
-@deffn procedure dispatch-tag? object
-Returns @samp{#t} if @var{object} is a dispatch tag, and @samp{#f}
-otherwise.
-@end deffn
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