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Edit `Adding Methods to Generic Functions'
* doc/ref/goops.texi (Adding Methods to Generic Functions): Move the bit about no applicable methods to `Invoking Generic Functions'. Other minor edits. (Basic Method Definition): Flattened into parent. (Method Definition Internals): Moved to MOP section at end of chapter.
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Neil Jerram
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1 changed files with 101 additions and 109 deletions
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@ -892,15 +892,7 @@ to that descendant's ancestors too.
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@node Adding Methods to Generic Functions
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@section Adding Methods to Generic Functions
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@menu
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* Basic Method Definition::
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* Method Definition Internals::
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@end menu
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@node Basic Method Definition
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@subsection Basic Method Definition
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To add a method to a generic function, use the @code{define-method} form.
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To add a method to a generic function, use @code{define-method}.
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@deffn syntax define-method (generic parameter @dots{}) . body
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Define a method for the generic function or accessor @var{generic} with
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@ -924,14 +916,14 @@ can be applied.
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@var{body} is the body of the method definition.
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@end deffn
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@code{define-method} expressions look a little like normal Scheme
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procedure definitions of the form
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@code{define-method} expressions look a little like Scheme procedure
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definitions of the form
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@example
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(define (name formals @dots{}) . body)
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@end example
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The most important difference is that each formal parameter, apart from the
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The important difference is that each formal parameter, apart from the
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possible ``rest'' argument, can be qualified by a class name:
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@code{@var{formal}} becomes @code{(@var{formal} @var{class})}. The
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meaning of this qualification is that the method being defined
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@ -951,97 +943,6 @@ only applicable to invocations of its generic function that have two
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parameters where the first parameter is an instance of the
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@code{<square>} class and the second parameter is a number.
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If a generic function is invoked with a combination of parameters for which
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there is no applicable method, GOOPS raises an error. For more about
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invocation error handling, and generic function invocation in general,
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see @ref{Invoking Generic Functions}.
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@node Method Definition Internals
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@subsection Method Definition Internals
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@code{define-method}
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@itemize @bullet
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@item
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checks the form of the first parameter, and applies the following steps
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to the accessor's setter if it has the @code{(setter @dots{})} form
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@item
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interpolates a call to @code{define-generic} or @code{define-accessor}
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if a generic function is not already defined with the supplied name
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@item
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calls @code{method} with the @var{parameter}s and @var{body}, to make a
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new method instance
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@item
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calls @code{add-method!} to add this method to the relevant generic
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function.
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@end itemize
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@deffn syntax method (parameter @dots{}) . body
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Make a method whose specializers are defined by the classes in
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@var{parameter}s and whose procedure definition is constructed from the
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@var{parameter} symbols and @var{body} forms.
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The @var{parameter} and @var{body} parameters should be as for
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@code{define-method} (@pxref{Basic Method Definition,, define-method}).
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@end deffn
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@code{method}
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@itemize @bullet
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@item
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extracts formals and specializing classes from the @var{parameter}s,
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defaulting the class for unspecialized parameters to @code{<top>}
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@item
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creates a closure using the formals and the @var{body} forms
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@item
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calls @code{make} with metaclass @code{<method>} and the specializers
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and closure using the @code{#:specializers} and @code{#:procedure}
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keywords.
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@end itemize
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@deffn procedure make-method specializers procedure
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Make a method using @var{specializers} and @var{procedure}.
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@var{specializers} should be a list of classes that specifies the
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parameter combinations to which this method will be applicable.
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@var{procedure} should be the closure that will applied to the generic
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function parameters when this method is invoked.
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@end deffn
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@code{make-method} is a simple wrapper around @code{make} with metaclass
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@code{<method>}.
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@deffn generic add-method! target method
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Generic function for adding method @var{method} to @var{target}.
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@end deffn
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@deffn method add-method! (generic <generic>) (method <method>)
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Add method @var{method} to the generic function @var{generic}.
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@end deffn
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@deffn method add-method! (proc <procedure>) (method <method>)
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If @var{proc} is a procedure with generic capability (@pxref{Extending
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Primitives,, generic-capability?}), upgrade it to a primitive generic
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and add @var{method} to its generic function definition.
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@end deffn
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@deffn method add-method! (pg <primitive-generic>) (method <method>)
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Add method @var{method} to the generic function definition of @var{pg}.
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Implementation: @code{(add-method! (primitive-generic-generic pg) method)}.
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@end deffn
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@deffn method add-method! (whatever <top>) (method <method>)
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Raise an error indicating that @var{whatever} is not a valid generic
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function.
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@end deffn
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@node Invoking Generic Functions
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@section Invoking Generic Functions
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@ -1052,12 +953,15 @@ the remaining elements of the list. [ *fixme* How do I put this in a
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more Schemely and less Lispy way? ]
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Usually a generic function contains several method definitions, with
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varying degrees of formal parameter specialization (@pxref{Basic
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Method Definition,, define-method}). So it is necessary to sort these
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methods by specificity with respect to the supplied arguments, and then
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apply the most specific method definition. Less specific methods
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may be applied subsequently if a method that is being applied calls
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@code{next-method}.
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varying degrees of formal parameter specialization (@pxref{Adding
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Methods to Generic Functions,, define-method}). So it is necessary to
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sort these methods by specificity with respect to the supplied
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arguments, and then apply the most specific method definition. Less
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specific methods may be applied subsequently if a method that is being
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applied calls @code{next-method}.
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If a generic function is invoked with a combination of parameters for
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which there is no applicable method, GOOPS raises an error.
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@menu
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* Determining Which Methods to Apply::
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@ -1689,6 +1593,7 @@ GOOPS' power, by customizing the behaviour of GOOPS itself.
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* Customizing Instance Creation::
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* Class Redefinition::
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* Method Definition::
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* Method Definition Internals::
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* Generic Function Internals::
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* Generic Function Invocation::
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@end menu
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@ -2575,6 +2480,93 @@ By defining further methods for @code{add-method!}, you can
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theoretically handle adding methods to further types of target.
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@end itemize
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@node Method Definition Internals
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@subsection Method Definition Internals
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@code{define-method}
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@itemize @bullet
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@item
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checks the form of the first parameter, and applies the following steps
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to the accessor's setter if it has the @code{(setter @dots{})} form
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@item
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interpolates a call to @code{define-generic} or @code{define-accessor}
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if a generic function is not already defined with the supplied name
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@item
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calls @code{method} with the @var{parameter}s and @var{body}, to make a
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new method instance
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@item
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calls @code{add-method!} to add this method to the relevant generic
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function.
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@end itemize
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@deffn syntax method (parameter @dots{}) . body
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Make a method whose specializers are defined by the classes in
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@var{parameter}s and whose procedure definition is constructed from the
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@var{parameter} symbols and @var{body} forms.
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The @var{parameter} and @var{body} parameters should be as for
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@code{define-method} (@pxref{Adding Methods to Generic Functions,,
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define-method}).
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@end deffn
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@code{method}
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@itemize @bullet
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@item
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extracts formals and specializing classes from the @var{parameter}s,
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defaulting the class for unspecialized parameters to @code{<top>}
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@item
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creates a closure using the formals and the @var{body} forms
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@item
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calls @code{make} with metaclass @code{<method>} and the specializers
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and closure using the @code{#:specializers} and @code{#:procedure}
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keywords.
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@end itemize
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@deffn procedure make-method specializers procedure
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Make a method using @var{specializers} and @var{procedure}.
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@var{specializers} should be a list of classes that specifies the
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parameter combinations to which this method will be applicable.
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@var{procedure} should be the closure that will applied to the generic
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function parameters when this method is invoked.
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@end deffn
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@code{make-method} is a simple wrapper around @code{make} with metaclass
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@code{<method>}.
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@deffn generic add-method! target method
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Generic function for adding method @var{method} to @var{target}.
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@end deffn
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@deffn method add-method! (generic <generic>) (method <method>)
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Add method @var{method} to the generic function @var{generic}.
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@end deffn
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@deffn method add-method! (proc <procedure>) (method <method>)
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If @var{proc} is a procedure with generic capability (@pxref{Extending
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Primitives,, generic-capability?}), upgrade it to a primitive generic
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and add @var{method} to its generic function definition.
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@end deffn
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@deffn method add-method! (pg <primitive-generic>) (method <method>)
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Add method @var{method} to the generic function definition of @var{pg}.
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Implementation: @code{(add-method! (primitive-generic-generic pg) method)}.
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@end deffn
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@deffn method add-method! (whatever <top>) (method <method>)
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Raise an error indicating that @var{whatever} is not a valid generic
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function.
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@end deffn
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@node Generic Function Internals
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@subsection Generic Function Internals
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