view classes.lisp @ 1:cbb5b478307e

Initial import of classes.lisp and default-methods.lisp from David.

darcs-hash:20061016144427-aa3d6-93919f5153445ade41eb753434da6f3c838c155a.gz

;; basic musical object classes

(defclass composition ()
  ())

(defclass event ()
  ())

(defclass pitched-event (event)
  ())

;; pitch-related classes

(defclass pitch ()
  ())

(defclass chromatic-pitch (pitch)
  ())

(defclass diatonic-pitch (pitch)
  ())

(defclass frequency (pitch)
  ())

(defclass interval ()
  ())

;; time-related classes

(defclass moment ()
  ())

(defclass duration ()
  ())

;; Some conditions we might want to be able to signal

(define-condition undefined-action (condition)
  ;; This condition would apply to an attempt to perform a meaningless
  ;; operation on an object. This may, initially, include things that
  ;; are a pain to implement but should really be used when it's
  ;; genuinely unclear what an operation means in the given
  ;; context. In such cases, a condition handler might be the best
  ;; approach anyway.
  ((operation :initarg :operation
	      :reader undefined-action-operation)
   (datatype :initarg :datatype
	     :reader undefined-action-datatype))
  (:report (lambda (condition stream)
	     (format stream "The consequence of performing ~A on and object of type ~A is undefined"
		     (undefined-action-operation condition)
		     (undefined-action-datatype condition)))

(define-condition insufficient-information (condition)
  ;; It should be possible to construct genuinely minimal musical
  ;; structures. When the information in these is insufficient to
  ;; answer a query, this condition should be raised.
  ((operation :initarg :operation
	      :reader insufficient-information-operation)
   (datatype :initarg :datatype
	     :reader insufficient-information-datatype))
  (:report (lambda (condition stream)
	     (format stream "The ~A object does not contain enough information to perform ~A"
		     (insufficient-information-datatype condition)
		     (insufficient-information-operation condition)))