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Move `Introspection' earlier

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* doc/ref/goops.texi (Introspection): Move to after `Generic Functions
  and Methods'.  The idea is to have all of that sections that make
  sense without needing to understand the MOP, before sections that
  really depend on the MOP.
This commit is contained in:
Neil Jerram 2011-01-14 19:08:46 +00:00
parent 68f4fee187
commit 62d7cba3d5
1 changed files with 280 additions and 279 deletions
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doc/ref/goops.texi
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@ -44,12 +44,12 @@ module. You can do this at the Guile REPL by evaluating:
* Slot Description Example:: * Slot Description Example::
* Methods and Generic Functions:: * Methods and Generic Functions::
* Inheritance:: * Inheritance::
* Introspection::
* Class Options:: * Class Options::
* Accessing Slots:: * Accessing Slots::
* Generic Functions and Accessors:: * Generic Functions and Accessors::
* Redefining a Class:: * Redefining a Class::
* Changing the Class of an Instance:: * Changing the Class of an Instance::
* Introspection::
* GOOPS Error Handling:: * GOOPS Error Handling::
* Object Comparisons:: * Object Comparisons::
* Cloning Objects:: * Cloning Objects::
@ -1237,6 +1237,285 @@ actual class C, if C1 comes before C2 in C's class precedence list.
@end itemize @end itemize
@node Introspection
@section Introspection
@dfn{Introspection}, also known as @dfn{reflection}, is the name given
to the ability to obtain information dynamically about GOOPS metaobjects.
It is perhaps best illustrated by considering an object oriented language
that does not provide any introspection, namely C++.
Nothing in C++ allows a running program to obtain answers to the following
types of question:
@itemize @bullet
@item
What are the data members of this object or class?
@item
What classes does this class inherit from?
@item
Is this method call virtual or non-virtual?
@item
If I invoke @code{Employee::adjustHoliday()}, what class contains the
@code{adjustHoliday()} method that will be applied?
@end itemize
In C++, answers to such questions can only be determined by looking at
the source code, if you have access to it. GOOPS, on the other hand,
includes procedures that allow answers to these questions --- or their
GOOPS equivalents --- to be obtained dynamically, at run time.
@menu
* Classes::
* Slots::
* Instances::
* Built-in classes::
* Generic Functions::
* Generic Function Methods::
@end menu
@node Classes
@subsection Classes
@deffn {primitive procedure} class-name class
Return the name of class @var{class}.
This is the value of the @var{class} metaobject's @code{name} slot.
@end deffn
@deffn {primitive procedure} class-direct-supers class
Return a list containing the direct superclasses of @var{class}.
This is the value of the @var{class} metaobject's
@code{direct-supers} slot.
@end deffn
@deffn {primitive procedure} class-direct-slots class
Return a list containing the slot definitions of the direct slots of
@var{class}.
This is the value of the @var{class} metaobject's @code{direct-slots}
slot.
@end deffn
@deffn {primitive procedure} class-direct-subclasses class
Return a list containing the direct subclasses of @var{class}.
This is the value of the @var{class} metaobject's
@code{direct-subclasses} slot.
@end deffn
@deffn {primitive procedure} class-direct-methods class
Return a list of all the generic function methods that use @var{class}
as a formal parameter specializer.
This is the value of the @var{class} metaobject's @code{direct-methods}
slot.
@end deffn
@deffn {primitive procedure} class-precedence-list class
Return the class precedence list for class @var{class} (@pxref{Class
Precedence List}).
This is the value of the @var{class} metaobject's @code{cpl} slot.
@end deffn
@deffn {primitive procedure} class-slots class
Return a list containing the slot definitions for all @var{class}'s slots,
including any slots that are inherited from superclasses.
This is the value of the @var{class} metaobject's @code{slots} slot.
@end deffn
@deffn {primitive procedure} class-environment class
Return the value of @var{class}'s @code{environment} slot.
[ *fixme* I don't know what this value is used for. ]
@end deffn
@deffn procedure class-subclasses class
Return a list of all subclasses of @var{class}.
@end deffn
@deffn procedure class-methods class
Return a list of all methods that use @var{class} or a subclass of
@var{class} as one of its formal parameter specializers.
@end deffn
@node Slots
@subsection Slots
@deffn procedure class-slot-definition class slot-name
Return the slot definition for the slot named @var{slot-name} in class
@var{class}. @var{slot-name} should be a symbol.
@end deffn
@deffn procedure slot-definition-name slot-def
Extract and return the slot name from @var{slot-def}.
@end deffn
@deffn procedure slot-definition-options slot-def
Extract and return the slot options from @var{slot-def}.
@end deffn
@deffn procedure slot-definition-allocation slot-def
Extract and return the slot allocation option from @var{slot-def}. This
is the value of the @code{#:allocation} keyword (@pxref{Slot Options,,
allocation}), or @code{#:instance} if the @code{#:allocation} keyword is
absent.
@end deffn
@deffn procedure slot-definition-getter slot-def
Extract and return the slot getter option from @var{slot-def}. This is
the value of the @code{#:getter} keyword (@pxref{Slot Options,,
getter}), or @code{#f} if the @code{#:getter} keyword is absent.
@end deffn
@deffn procedure slot-definition-setter slot-def
Extract and return the slot setter option from @var{slot-def}. This is
the value of the @code{#:setter} keyword (@pxref{Slot Options,,
setter}), or @code{#f} if the @code{#:setter} keyword is absent.
@end deffn
@deffn procedure slot-definition-accessor slot-def
Extract and return the slot accessor option from @var{slot-def}. This
is the value of the @code{#:accessor} keyword (@pxref{Slot Options,,
accessor}), or @code{#f} if the @code{#:accessor} keyword is absent.
@end deffn
@deffn procedure slot-definition-init-value slot-def
Extract and return the slot init-value option from @var{slot-def}. This
is the value of the @code{#:init-value} keyword (@pxref{Slot Options,,
init-value}), or the unbound value if the @code{#:init-value} keyword is
absent.
@end deffn
@deffn procedure slot-definition-init-form slot-def
Extract and return the slot init-form option from @var{slot-def}. This
is the value of the @code{#:init-form} keyword (@pxref{Slot Options,,
init-form}), or the unbound value if the @code{#:init-form} keyword is
absent.
@end deffn
@deffn procedure slot-definition-init-thunk slot-def
Extract and return the slot init-thunk option from @var{slot-def}. This
is the value of the @code{#:init-thunk} keyword (@pxref{Slot Options,,
init-thunk}), or @code{#f} if the @code{#:init-thunk} keyword is absent.
@end deffn
@deffn procedure slot-definition-init-keyword slot-def
Extract and return the slot init-keyword option from @var{slot-def}.
This is the value of the @code{#:init-keyword} keyword (@pxref{Slot
Options,, init-keyword}), or @code{#f} if the @code{#:init-keyword}
keyword is absent.
@end deffn
@deffn procedure slot-init-function class slot-name
Return the initialization function for the slot named @var{slot-name} in
class @var{class}. @var{slot-name} should be a symbol.
The returned initialization function incorporates the effects of the
standard @code{#:init-thunk}, @code{#:init-form} and @code{#:init-value}
slot options. These initializations can be overridden by the
@code{#:init-keyword} slot option or by a specialized @code{initialize}
method, so, in general, the function returned by
@code{slot-init-function} may be irrelevant. For a fuller discussion,
see @ref{Slot Options,, init-value}.
@end deffn
@node Instances
@subsection Instances
@deffn {primitive procedure} class-of value
Return the GOOPS class of any Scheme @var{value}.
@end deffn
@deffn {primitive procedure} instance? object
Return @code{#t} if @var{object} is any GOOPS instance, otherwise
@code{#f}.
@end deffn
@deffn procedure is-a? object class
Return @code{#t} if @var{object} is an instance of @var{class} or one of
its subclasses.
@end deffn
Implementation notes: @code{is-a?} uses @code{class-of} and
@code{class-precedence-list} to obtain the class precedence list for
@var{object}.
@node Built-in classes
@subsection Built-in classes
There are built-in classes like @code{<string>}, @code{<list>} and
@code{<number>} corresponding to all the Guile Scheme types. You can
use the @code{is-a?} predicate to ask whether any given value belongs to
a given class, or @code{class-of} to discover the class of a given
value.
@lisp
(is-a? 2.3 <number>) @result{} #t
(is-a? 2.3 <real>) @result{} #t
(is-a? 2.3 <string>) @result{} #f
(is-a? '("a" "b") <string>) @result{} #f
(is-a? '("a" "b") <list>) @result{} #t
(is-a? (car '("a" "b")) <string>) @result{} #t
(is-a? <string> <class>) @result{} #t
(is-a? <class> <string>) @result{} #f
(class-of 2.3) @result{} #<<class> <real> 908c708>
(class-of #(1 2 3)) @result{} #<<class> <vector> 908cd20>
(class-of <string>) @result{} #<<class> <class> 8bd3e10>
(class-of <class>) @result{} #<<class> <class> 8bd3e10>
@end lisp
@node Generic Functions
@subsection Generic Functions
@deffn {primitive procedure} generic-function-name gf
Return the name of generic function @var{gf}.
@end deffn
@deffn {primitive procedure} generic-function-methods gf
Return a list of the methods of generic function @var{gf}.
This is the value of the @var{gf} metaobject's @code{methods} slot.
@end deffn
@node Generic Function Methods
@subsection Generic Function Methods
@deffn {primitive procedure} method-generic-function method
Return the generic function that @var{method} belongs to.
This is the value of the @var{method} metaobject's
@code{generic-function} slot.
@end deffn
@deffn {primitive procedure} method-specializers method
Return a list of @var{method}'s formal parameter specializers .
This is the value of the @var{method} metaobject's
@code{specializers} slot.
@end deffn
@deffn {primitive procedure} method-procedure method
Return the procedure that implements @var{method}.
This is the value of the @var{method} metaobject's
@code{procedure} slot.
@end deffn
@deffn generic method-source
@deffnx method method-source (m <method>)
Return an expression that prints to show the definition of method
@var{m}.
@example
(define-generic cube)
(define-method (cube (n <number>))
(* n n n))
(map method-source (generic-function-methods cube))
@result{}
((method ((n <number>)) (* n n n)))
@end example
@end deffn
@node Class Options @node Class Options
@section Class Options @section Class Options
@ -1636,284 +1915,6 @@ class redefinition behaviour is not overridden, GOOPS (eventually)
invokes the @code{change-class} generic function for each existing invokes the @code{change-class} generic function for each existing
instance of the redefined class. instance of the redefined class.
@node Introspection
@section Introspection
@dfn{Introspection}, also known as @dfn{reflection}, is the name given
to the ability to obtain information dynamically about GOOPS metaobjects.
It is perhaps best illustrated by considering an object oriented language
that does not provide any introspection, namely C++.
Nothing in C++ allows a running program to obtain answers to the following
types of question:
@itemize @bullet
@item
What are the data members of this object or class?
@item
What classes does this class inherit from?
@item
Is this method call virtual or non-virtual?
@item
If I invoke @code{Employee::adjustHoliday()}, what class contains the
@code{adjustHoliday()} method that will be applied?
@end itemize
In C++, answers to such questions can only be determined by looking at
the source code, if you have access to it. GOOPS, on the other hand,
includes procedures that allow answers to these questions --- or their
GOOPS equivalents --- to be obtained dynamically, at run time.
@menu
* Classes::
* Slots::
* Instances::
* Built-in classes::
* Generic Functions::
* Generic Function Methods::
@end menu
@node Classes
@subsection Classes
@deffn {primitive procedure} class-name class
Return the name of class @var{class}.
This is the value of the @var{class} metaobject's @code{name} slot.
@end deffn
@deffn {primitive procedure} class-direct-supers class
Return a list containing the direct superclasses of @var{class}.
This is the value of the @var{class} metaobject's
@code{direct-supers} slot.
@end deffn
@deffn {primitive procedure} class-direct-slots class
Return a list containing the slot definitions of the direct slots of
@var{class}.
This is the value of the @var{class} metaobject's @code{direct-slots}
slot.
@end deffn
@deffn {primitive procedure} class-direct-subclasses class
Return a list containing the direct subclasses of @var{class}.
This is the value of the @var{class} metaobject's
@code{direct-subclasses} slot.
@end deffn
@deffn {primitive procedure} class-direct-methods class
Return a list of all the generic function methods that use @var{class}
as a formal parameter specializer.
This is the value of the @var{class} metaobject's @code{direct-methods}
slot.
@end deffn
@deffn {primitive procedure} class-precedence-list class
Return the class precedence list for class @var{class} (@pxref{Class
Precedence List}).
This is the value of the @var{class} metaobject's @code{cpl} slot.
@end deffn
@deffn {primitive procedure} class-slots class
Return a list containing the slot definitions for all @var{class}'s slots,
including any slots that are inherited from superclasses.
This is the value of the @var{class} metaobject's @code{slots} slot.
@end deffn
@deffn {primitive procedure} class-environment class
Return the value of @var{class}'s @code{environment} slot.
[ *fixme* I don't know what this value is used for. ]
@end deffn
@deffn procedure class-subclasses class
Return a list of all subclasses of @var{class}.
@end deffn
@deffn procedure class-methods class
Return a list of all methods that use @var{class} or a subclass of
@var{class} as one of its formal parameter specializers.
@end deffn
@node Slots
@subsection Slots
@deffn procedure class-slot-definition class slot-name
Return the slot definition for the slot named @var{slot-name} in class
@var{class}. @var{slot-name} should be a symbol.
@end deffn
@deffn procedure slot-definition-name slot-def
Extract and return the slot name from @var{slot-def}.
@end deffn
@deffn procedure slot-definition-options slot-def
Extract and return the slot options from @var{slot-def}.
@end deffn
@deffn procedure slot-definition-allocation slot-def
Extract and return the slot allocation option from @var{slot-def}. This
is the value of the @code{#:allocation} keyword (@pxref{Slot Options,,
allocation}), or @code{#:instance} if the @code{#:allocation} keyword is
absent.
@end deffn
@deffn procedure slot-definition-getter slot-def
Extract and return the slot getter option from @var{slot-def}. This is
the value of the @code{#:getter} keyword (@pxref{Slot Options,,
getter}), or @code{#f} if the @code{#:getter} keyword is absent.
@end deffn
@deffn procedure slot-definition-setter slot-def
Extract and return the slot setter option from @var{slot-def}. This is
the value of the @code{#:setter} keyword (@pxref{Slot Options,,
setter}), or @code{#f} if the @code{#:setter} keyword is absent.
@end deffn
@deffn procedure slot-definition-accessor slot-def
Extract and return the slot accessor option from @var{slot-def}. This
is the value of the @code{#:accessor} keyword (@pxref{Slot Options,,
accessor}), or @code{#f} if the @code{#:accessor} keyword is absent.
@end deffn
@deffn procedure slot-definition-init-value slot-def
Extract and return the slot init-value option from @var{slot-def}. This
is the value of the @code{#:init-value} keyword (@pxref{Slot Options,,
init-value}), or the unbound value if the @code{#:init-value} keyword is
absent.
@end deffn
@deffn procedure slot-definition-init-form slot-def
Extract and return the slot init-form option from @var{slot-def}. This
is the value of the @code{#:init-form} keyword (@pxref{Slot Options,,
init-form}), or the unbound value if the @code{#:init-form} keyword is
absent.
@end deffn
@deffn procedure slot-definition-init-thunk slot-def
Extract and return the slot init-thunk option from @var{slot-def}. This
is the value of the @code{#:init-thunk} keyword (@pxref{Slot Options,,
init-thunk}), or @code{#f} if the @code{#:init-thunk} keyword is absent.
@end deffn
@deffn procedure slot-definition-init-keyword slot-def
Extract and return the slot init-keyword option from @var{slot-def}.
This is the value of the @code{#:init-keyword} keyword (@pxref{Slot
Options,, init-keyword}), or @code{#f} if the @code{#:init-keyword}
keyword is absent.
@end deffn
@deffn procedure slot-init-function class slot-name
Return the initialization function for the slot named @var{slot-name} in
class @var{class}. @var{slot-name} should be a symbol.
The returned initialization function incorporates the effects of the
standard @code{#:init-thunk}, @code{#:init-form} and @code{#:init-value}
slot options. These initializations can be overridden by the
@code{#:init-keyword} slot option or by a specialized @code{initialize}
method, so, in general, the function returned by
@code{slot-init-function} may be irrelevant. For a fuller discussion,
see @ref{Slot Options,, init-value}.
@end deffn
@node Instances
@subsection Instances
@deffn {primitive procedure} class-of value
Return the GOOPS class of any Scheme @var{value}.
@end deffn
@deffn {primitive procedure} instance? object
Return @code{#t} if @var{object} is any GOOPS instance, otherwise
@code{#f}.
@end deffn
@deffn procedure is-a? object class
Return @code{#t} if @var{object} is an instance of @var{class} or one of
its subclasses.
@end deffn
Implementation notes: @code{is-a?} uses @code{class-of} and
@code{class-precedence-list} to obtain the class precedence list for
@var{object}.
@node Built-in classes
@subsection Built-in classes
There are built-in classes like @code{<string>}, @code{<list>} and
@code{<number>} corresponding to all the Guile Scheme types. You can
use the @code{is-a?} predicate to ask whether any given value belongs to
a given class, or @code{class-of} to discover the class of a given
value.
@lisp
(is-a? 2.3 <number>) @result{} #t
(is-a? 2.3 <real>) @result{} #t
(is-a? 2.3 <string>) @result{} #f
(is-a? '("a" "b") <string>) @result{} #f
(is-a? '("a" "b") <list>) @result{} #t
(is-a? (car '("a" "b")) <string>) @result{} #t
(is-a? <string> <class>) @result{} #t
(is-a? <class> <string>) @result{} #f
(class-of 2.3) @result{} #<<class> <real> 908c708>
(class-of #(1 2 3)) @result{} #<<class> <vector> 908cd20>
(class-of <string>) @result{} #<<class> <class> 8bd3e10>
(class-of <class>) @result{} #<<class> <class> 8bd3e10>
@end lisp
@node Generic Functions
@subsection Generic Functions
@deffn {primitive procedure} generic-function-name gf
Return the name of generic function @var{gf}.
@end deffn
@deffn {primitive procedure} generic-function-methods gf
Return a list of the methods of generic function @var{gf}.
This is the value of the @var{gf} metaobject's @code{methods} slot.
@end deffn
@node Generic Function Methods
@subsection Generic Function Methods
@deffn {primitive procedure} method-generic-function method
Return the generic function that @var{method} belongs to.
This is the value of the @var{method} metaobject's
@code{generic-function} slot.
@end deffn
@deffn {primitive procedure} method-specializers method
Return a list of @var{method}'s formal parameter specializers .
This is the value of the @var{method} metaobject's
@code{specializers} slot.
@end deffn
@deffn {primitive procedure} method-procedure method
Return the procedure that implements @var{method}.
This is the value of the @var{method} metaobject's
@code{procedure} slot.
@end deffn
@deffn generic method-source
@deffnx method method-source (m <method>)
Return an expression that prints to show the definition of method
@var{m}.
@example
(define-generic cube)
(define-method (cube (n <number>))
(* n n n))
(map method-source (generic-function-methods cube))
@result{}
((method ((n <number>)) (* n n n)))
@end example
@end deffn
@node GOOPS Error Handling @node GOOPS Error Handling
@section Error Handling @section Error Handling