You are looking at historical revision 19346 of this page. It may differ significantly from its current revision.
- Defining forms
- Base language
- Intercessory protocol
- Additional protocol
- Utility procedures
- Builtin classes
- <byte-vector> ; DEPRECATED
- Extending class-of
- Version History
This extension is a port of Gregor Kiczales TinyCLOS with numerous modifications.
Note: you might consider taking a look at coops for a more up-to-date CLOS-like object system for CHICKEN.
define-class[syntax] (define-class NAME (SUPERCLASS1 ...) (SLOTNAME1 ...) [METACLASS])
Sets the variable NAME to a new class (a new instance of the class <class>). SUPERCLASS1 ... is a list of superclasses of the newly created class. If no superclasses are given, then <object> is assumed. SLOTNAME1 ... are the names of the direct slots of the class. if METACLASS is provided, then the new class-instance is an instance of METACLASS instead of <class>.
(define-class NAME (SUPER) (SLOT1 SLOT2) META)
is equivalent to
(define NAME (make META 'name 'NAME 'direct-supers (list SUPER) 'direct-slots (list 'SLOT1 'SLOT2)) )
Note that slots-names are not required to be symbols, so the following is perfectly valid:
(define hidden-slot (list 'hidden)) (define <myclass> (make <class> 'direct-supers (list <object>) 'direct-slots (list hidden-slot) ) ) (define x1 (make <myclass>) (slot-set! x1 hidden-slot 99)
To exploit this, however, the MAKE form has to be used as above. define-class only supports symbolic slot names.
By convention, identifiers bound to classes in TinyCLOS are denoted by angle brackets as above. This is not required, however. A class may be bound to any identifier without affecting the behavior of the system.
define-generic[syntax] (define-generic NAME [CLASS])
Binds the variable NAME to a fresh generic function object without associated methods. If the optional argument CLASS is given, then the generic function will be an instance of that class.
The new generic function cannot be called until appropriate methods are defined. To do that, use add-method or define-method.
define-method[syntax] (define-method (NAME (VARIABLE1 CLASS1) ... PARAMETERS ...) BODY ...)
Adds a new method with the code BODY ... to the generic function bound to NAME. CLASS1 ... is a list if classes that specialize this particular method. The method can have additional parameters PARAMETERS, which do not specialize the method any further. Extended lambda-lists are allowed (#!optional, #!key or #!rest argument lists), but can not be specialized. Inside the body of the method the identifier call-next-method names a procedure of zero arguments that can be invoked to call the next applicable method with the same arguments.
; Create new generic (define-generic square-number?) ; ; Provide a method to operate on integers (define-method (square-number? (n <integer>)) (and (positive? n) (let ((sq (truncate (sqrt n)))) (= (* sq sq) n)))) ; ; Provide a method to operate on inexact numbers (define-method (square-number? (n <inexact>)) #f)
This example also shows that generics can be used without creating classes. It exploits the primitive class system of TinyCLOS, in which all Scheme objects are members of a built-in class hierarchy.
It is an error to use define-method if no generic function is bound to NAME. This is a change from previous versions of TinyCLOS.
Currently methods defined with define-method should not be hidden (via (declare (hide ...)), nor should such files be compiled in block mode, unless the methods are exported.
add-method[procedure] (add-method GENERIC METHOD)
Adds the method object METHOD to the list of applicable methods for the generic function GENERIC.
instance?[procedure] (instance? X)
Returns #t if X is an instance of a non-primitive class.
make[procedure] (make CLASS INITARG ...)
Creates a new instance of CLASS and passes INITARG ... to the initialize method of this class.
If CLASS is a primitive class, the result of this procedure is undefined.
make-class[procedure] (make-class SUPERCLASSES SLOTNAMES)
Creates a new class object, where SUPERCLASSES should be the list of direct superclass objects and SLOTNAMES should be a list of symbols naming the slots of this class.
define-class*[syntax] (define-class* (SUPERCLASS1 ...) (SLOTNAME1 ...) [METACLASS])
This macro returns a new anonymous class defined using syntax similar to define-class. As in define-class the superclass and slotname lists are not quoted.
(let ((CLASS (define-class* (SUPER) (SLOT1 SLOT2) METACLASS))) ...)
is equivalent to
(let ((CLASS (make METACLASS (list SUPER) (list 'SLOT1 'SLOT2)))) ...)
(let ((CLASS (define-class* () (SLOT1 SLOT2)))) ...)
is equivalent to
(let ((CLASS (make <class> (list <object>) (list 'SLOT1 'SLOT2)))) ...)
make-generic[procedure] (make-generic [NAME])
Creates a new generic function object. If NAME is specified, then it should be a string.
make-method[procedure] (make-method SPECIALIZERS PROC)
Creates a new method object specialized to the list of classes in SPECIALIZERS.
(define-method (foo (x <bar>)) 123) <=> (add-method foo (make-method (list <bar>) (lambda (call-next-method x) 123)))
slot-ref[procedure] (slot-ref INSTANCE SLOTNAME)
Returns the value of the slot SLOTNAME of the object INSTANCE.
slot-set![procedure] (slot-set! INSTANCE SLOTNAME VALUE)
[setter] (set! (slot-ref INSTANCE SLOTNAME) VALUE)
Sets the value of the slot SLOTNAME of the object INSTANCE to VALUE.
slot@[syntax] (slot@ OBJECT SLOTNAME ... [= VALUE])
Object slots are de-referenced by name left-to-right, with an optional last slot assignment.
(slot@ foo x y) ;=> (slot-ref (slot-ref foo 'x) 'y) (slot@ foo x y = "bar") ;=> (slot-set! (slot-ref foo 'x) 'y "bar")
class-cpl[procedure] (class-cpl CLASS)
Returns the class-precedence-list of CLASS as a list of classes.
class-direct-slots[procedure] (class-direct-slots CLASS)
Returns the list of direct slots of CLASS as a list of lists, where each sublist contains the name of the slot.
class-direct-supers[procedure] (class-direct-supers CLASS)
Returns the list of direct superclasses of CLASS.
class-of[procedure] (class-of X)
Returns the class that the object X is an instance of.
See Extensions below for an API to extend the set of "built-in" classes.
class-name[procedure] (class-name CLASS)
Returns name of CLASS.
class-slots[procedure] (class-slots CLASS)
Returns the list of all slots of CLASS and its superclasses as a list of lists, where each sublist contains the name of the slot.
generic-methods[procedure] (generic-methods GENERIC)
Returns the list of all methods associated with the generic function GENERIC.
method-specializers[procedure] (method-specializers METHOD)
Returns the list of classes that specialize METHOD.
method-procedure[procedure] (method-procedure METHOD)
Returns the procedure that contains the body of METHOD.
subclass?[procedure] (subclass? CLASS1 CLASS2)
Returns #t is CLASS1 is a subclass of CLASS2, or #f otherwise. Note that the following holds:
(subclass? X X) ==> #t
instance-of?[procedure] (instance-of? X CLASS)
Returns #t if X is an instance of CLASS (or one of its subclasses).
These definitions allow interfacing to the Meta Object Protocol of TinyCLOS. For serious use, it is recommended to consult the source code (tinyclos.scm).
Allocates storage for an instance of CLASS and returns the instance.
Returns a procedure that will be called to apply the generic function methods to the arguments.
Returns a procedure of two arguments, a list of applicable methods and a list of arguments and applies the methods.
Returns a procedure of one argument. The procedure is called with the list of actual arguments passed to the generic function and should return a list of applicable methods, sorted by precedence.
Computes and returns the class-precedence-list of CLASS.
<generic>(compute-getter-and-setter CLASS SLOT ALLOCATOR)</generic>
Returns two values, the procedures that get and set the contents of the slot SLOT. ALLOCATOR is a procedure of one argument that gets an initializer function and returns the getter and setter procedures for the allocated slot.
Returns a procedure of three arguments (two methods and a list of arguments) that returns #t if the first method is more specific than the second one with respect to the list of arguments. Otherwise the returned predicate returns #f.
Computes and returns the list of slots of CLASS.
<generic>(initialize INSTANCE INITARGS)</generic>
Initializes the object INSTANCE. INITARGS is the list of initialization arguments that were passed to the make procedure.
<generic>(describe-object OBJECT [PORT])</generic>
Writes a description of OBJECT to PORT. If PORT is not given it defaults to the value of (current-output-port).
If given an instance, this procedure will identify the class to which the instance belongs and list the names and values of all its slots. If given a primitive, this procedure will identify the primitive class to which the argument belongs.
(define-class <person> () (name age)) (define-class <customer> (<person>) (last-contact-date purchases customer-number)) (define-method (initialize (p <person>) initargs ) (initialize-slots p initargs)) (define p1 (make <customer> 'name "John" 'purchases 12.80 'customer-number 11)) (describe-object p1) instance of class customer: last-contact-date -> #<unspecified> purchases -> 12.8 customer-number -> 11 name -> "John" age -> #<unspecified>
(describe-object 12) instance of primitive class exact
(describe-object (if #f '())) instance of primitive class void
<generic>(print-object INSTANCE [PORT])</generic>
Writes a textual representation of INSTANCE to PORT. Any output of an instance with display, write, and print will invoke this generic function. If PORT is not given it defaults to the value of (current-output-port).
initialize-slots[procedure] (initialize-slots INSTANCE INITARGS)
This procedure takes a sequence of alternating slot-names and initialization values in INITARGS and initializes the corresponding slots in INSTANCE.
(define-class <pos> () (x y)) (define-method (initialize (pos <pos>) initargs) (call-next-method) (initialize-slots pos initargs)) (define p1 (make <pos> 'x 1 'y 2)) (define p2 (make <pos> 'x 3 'y 5))
make/copy[procedure] (make/copy INSTANCE [INITARGS])
Returns a copy of the object INSTANCE. INITARGS is the list of initialization arguments that will override the INSTANCE copy slot values.
The class hierarchy of builtin classes looks like this:
<top> <object> <class> <procedure-class> <entity-class> <generic> <primitive-class> <procedure> <c++-object> <primitive> <void> <boolean> <symbol> <char> <vector> <pair> <number> <integer> <exact> <inexact> <string> <port> <input-port> <output-port> <pointer> <tagged-pointer> <swig-pointer> <locative> <blob> <byte-vector> ; DEPRECATED <structure> <u8vector> <s8vector> <u16vector> <s16vector> <u32vector> <s32vector> <f32vector> <f64vector> <char-set> <condition> <continuation> <environment> <hash-table> <lock> <mmap> <mutex> <promise> <queue> <read-table> <regexp> <tcp-listener> <thread> <time> <end-of-file>
The parent class of the classes of all primitive Scheme objects.
The classes of primitive Scheme objects.
<byte-vector> ; DEPRECATED
The classes of extended data types provided by the various library units.
The parent class of all class objects.
The parent class of objects that can be invoked as a procedure and have slots.
The parent class of generic function objects.
The parent class of method objects.
The parent class of all objects.
The parent class of objects that can be invoked as a procedure.
Class of condition objects.
Class of continuation objects captured by continuation-capture.
The classes of data objects provided by the various supplied SRFIs.
Classes of objects used in the posix library unit.
A machine pointer (untagged, tagged or pointing to SWIG-wrapped data).
The class of objects returned by delay.
The class of an object returned by tcp-listen.
The class of an object returned by regexp.
The class of generated wrappers for C++ classes parsed by the "easy" foreign function interface easyffi.
The class-of procedure can be extended to recognize additional classes beyond the built-in set.
The define-... macros below automatically converts the symbolic name of the type into the canonical form, i.e. surrounded by '<' and '>'. This is assuming too much on the behalf of the user. Should leave this up to the user.
define-primitive-class[syntax] (define-primitive-class NAME PREDICATE [SUPER-CLASS ...])
Defines a new primitive class, <NAME>, with type predicate procedure PREDICATE, and the super-classes SUPER-CLASS .... When a SUPER-CLASS is not specified the class <primitive> is assumed.
The PREDICATE procedure takes the object to test as the lone parameter, and returns #f for failure.
Any existing class with the same PREDICATE will be replaced![procedure] (new-primitive-class CLASS-NAME PREDICATE [SUPER-CLASS ...])
[procedure] (delete-primitive-class CLASS)
define-structure-class[syntax] (define-structure-class NAME TAG)
Defines a new structure class, <NAME>, with class-of structure type symbol TAG.
Any existing class with the same TAG will be replaced![procedure] (new-structure-class CLASS-NAME TAG)
[procedure] (delete-structure-class CLASS)
define-tagged-pointer-class[syntax] (define-tagged-pointer-class NAME TAG)
Defines a new tagged-pointer class, <NAME>, with class-of tagged-pointer type symbol TAG.
Any existing class with the same TAG will be replaced![procedure] (new-tagged-pointer-class CLASS-NAME TAG)
[procedure] (delete-tagged-pointer-class CLASS)
define-extended-procedure-class[syntax] (define-extended-procedure-class NAME PREDICATE)
Defines a new extended-procedure class, <NAME>, with type predicate procedure PREDICATE.
The PREDICATE procedure takes the extended-data to test as the lone parameter, and returns #f for failure.
Any existing class with the same PREDICATE will be replaced![procedure] (new-extended-procedure-class CLASS-NAME PREDICATE)
[procedure] (delete-extended-procedure-class CLASS)
Orignal version by Gregor Kiczales, CHICKEN port and performance enhancements by felix winkelmann, some of which have been inspired by Eli Barzilays Swindle
slot@ from the '@' macro by Dan Muresan.
Copyright (c) 2000-2007, Felix L. Winkelmann All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- Fix for extension of extended-procedure class-of. [Kon Lovett]
- exposed in repository
- define-generic now mandatory
- fixed use of obsolete reader hack
- added make/copy [Kon Lovett]
- added unbound error to class-of [Kon Lovett]
- fixed bug in class-of that caused crash when passed void [felix winkelmann]
- Uses ':optional' (for older Chicken) [Kon Lovett]
- Added class-of extension api, and slot@. Much internal re-ordering [Kon Lovett]
- removed unnecessary feature-registration [thanks to Matthew Welland]
- removed use of :optional in tinyclos.scm [thanks to Todd Ingalls]
- added missing syntax indicator in setup script
- moved from base distribution into separate extension