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This is the Macroless Object System written by Wade Humeniuk (whumeniu@datap.ca). Conceptual Tributes: Yasos, MacScheme’s %object, CLOS, Lack of R4RS macros.
An object is an ordered association-list (by eq?) of methods
(procedures). Methods can be added (make-method!), deleted
(unmake-method!) and retrieved (get-method). Objects may
inherit methods from other objects. The object binds to the environment
it was created in, allowing closures to be used to hide private
procedures and data.
A generic-method associates (in terms of eq?) object’s method.
This allows scheme function style to be used for objects. The calling
scheme for using a generic method is (generic-method object param1
param2 ...).
A method is a procedure that exists in the object. To use a method get-method must be called to look-up the method. Generic methods implement the get-method functionality. Methods may be added to an object associated with any scheme obj in terms of eq?
A generic method that returns a boolean value for any scheme obj.
A object’s method asscociated with a generic-predicate. Returns
#t.
Returns an object. Current object implementation is a tagged vector.
ancestors are optional and must be objects in terms of object?.
ancestors methods are included in the object. Multiple
ancestors might associate the same generic-method with a method.
In this case the method of the ancestor first appearing in the
list is the one returned by get-method.
Returns boolean value whether obj was created by make-object.
Returns a procedure which be associated with an object’s methods. If exception-procedure is specified then it is used to process non-objects.
Returns a boolean procedure for any scheme object.
Associates method to the generic-method in the object. The
method overrides any previous association with the
generic-method within the object. Using unmake-method!
will restore the object’s previous association with the
generic-method. method must be a procedure.
Makes a predicate method associated with the generic-predicate.
Removes an object’s association with a generic-method .
Returns the object’s method associated (if any) with the generic-method. If no associated method exists an error is flagged.
(require 'object) (define instantiate (make-generic-method)) (define (make-instance-object . ancestors) (define self (apply make-object (map (lambda (obj) (instantiate obj)) ancestors))) (make-method! self instantiate (lambda (self) self)) self) (define who (make-generic-method)) (define imigrate! (make-generic-method)) (define emigrate! (make-generic-method)) (define describe (make-generic-method)) (define name (make-generic-method)) (define address (make-generic-method)) (define members (make-generic-method)) (define society (let () (define self (make-instance-object)) (define population '()) (make-method! self imigrate! (lambda (new-person) (if (not (eq? new-person self)) (set! population (cons new-person population))))) (make-method! self emigrate! (lambda (person) (if (not (eq? person self)) (set! population (comlist:remove-if (lambda (member) (eq? member person)) population))))) (make-method! self describe (lambda (self) (map (lambda (person) (describe person)) population))) (make-method! self who (lambda (self) (map (lambda (person) (name person)) population))) (make-method! self members (lambda (self) population)) self)) (define (make-person %name %address) (define self (make-instance-object society)) (make-method! self name (lambda (self) %name)) (make-method! self address (lambda (self) %address)) (make-method! self who (lambda (self) (name self))) (make-method! self instantiate (lambda (self) (make-person (string-append (name self) "-son-of") %address))) (make-method! self describe (lambda (self) (list (name self) (address self)))) (imigrate! self) self)
Inheritance:
<inverter>::(<number> <description>)
Generic-methods
<inverter>::value ⇒ <number>::value
<inverter>::set-value! ⇒ <number>::set-value!
<inverter>::describe ⇒ <description>::describe
<inverter>::help
<inverter>::invert
<inverter>::inverter?
Inheritance
<number>::()
Slots
<number>::<x>
Generic Methods
<number>::value
<number>::set-value!
(require 'object) (define value (make-generic-method (lambda (val) val))) (define set-value! (make-generic-method)) (define invert (make-generic-method (lambda (val) (if (number? val) (/ 1 val) (error "Method not supported:" val))))) (define noop (make-generic-method)) (define inverter? (make-generic-predicate)) (define describe (make-generic-method)) (define help (make-generic-method)) (define (make-number x) (define self (make-object)) (make-method! self value (lambda (this) x)) (make-method! self set-value! (lambda (this new-value) (set! x new-value))) self) (define (make-description str) (define self (make-object)) (make-method! self describe (lambda (this) str)) (make-method! self help (lambda (this) "Help not available")) self) (define (make-inverter) (let* ((self (make-object (make-number 1) (make-description "A number which can be inverted"))) (<value> (get-method self value))) (make-method! self invert (lambda (self) (/ 1 (<value> self)))) (make-predicate! self inverter?) (unmake-method! self help) (make-method! self help (lambda (self) (display "Inverter Methods:") (newline) (display " (value inverter) ==> n") (newline))) self)) ;;;; Try it out (define invert! (make-generic-method)) (define x (make-inverter)) (make-method! x invert! (lambda (x) (set-value! x (/ 1 (value x))))) (value x) ⇒ 1 (set-value! x 33) ⇒ undefined (invert! x) ⇒ undefined (value x) ⇒ 1/33 (unmake-method! x invert!) ⇒ undefined (invert! x) error→ ERROR: Method not supported: x
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