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    Length: 2866 (0xb32)
    Types: TextFile
    Names: »wind.scm.85«

└─⟦a0efdde77⟧ Bits:30001252 EUUGD11 Tape, 1987 Spring Conference Helsinki
    └─⟦this⟧ »EUUGD11/gnu-31mar87/scheme/scm/wind.scm.85« 

TextFile

;;; -*-Scheme-*-
;;;
;;;	Copyright (c) 1984 Massachusetts Institute of Technology
;;;
;;;	This material was developed by the Scheme project at the
;;;	Massachusetts Institute of Technology, Department of
;;;	Electrical Engineering and Computer Science.  Permission to
;;;	copy this software, to redistribute it, and to use it for any
;;;	purpose is granted, subject to the following restrictions and
;;;	understandings.
;;;
;;;	1. Any copy made of this software must include this copyright
;;;	notice in full.
;;;
;;;	2. Users of this software agree to make their best efforts (a)
;;;	to return to the MIT Scheme project any improvements or
;;;	extensions that they make, so that these may be included in
;;;	future releases; and (b) to inform MIT of noteworthy uses of
;;;	this software.
;;;
;;;	3.  All materials developed as a consequence of the use of
;;;	this software shall duly acknowledge such use, in accordance
;;;	with the usual standards of acknowledging credit in academic
;;;	research.
;;;
;;;	4. MIT has made no warrantee or representation that the
;;;	operation of this software will be error-free, and MIT is
;;;	under no obligation to provide any services, by way of
;;;	maintenance, update, or otherwise.
;;;
;;;	5.  In conjunction with products arising from the use of this
;;;	material, there shall be no use of the name of the
;;;	Massachusetts Institute of Technology nor of any adaptation
;;;	thereof in any advertising, promotional, or sales literature
;;;	without prior written consent from MIT in each case.
;;;

;;;; State Space Model

(declare (usual-integrations)
	 (compilable-primitive-functions
	  set-fixed-objects-vector!))
\f


(vector-set! (get-fixed-objects-vector)
	     (fixed-objects-vector-slot 'STATE-SPACE-TAG)
	     '(STATE-SPACE))

(vector-set! (get-fixed-objects-vector)
	     (fixed-objects-vector-slot 'STATE-POINT-TAG)
	     '(STATE-POINT))

(set-fixed-objects-vector! (get-fixed-objects-vector))

(define make-state-space
  (make-primitive-procedure 'MAKE-STATE-SPACE))

;;; This wrapper is here because primitives can't have 4 arguments.

(define execute-at-new-state-point
  (let ((primitive (make-primitive-procedure 'EXECUTE-AT-NEW-STATE-POINT)))
    (named-lambda (execute-at-new-state-point space change restore body)
      (primitive space change (cons restore body)))))

(define translate-to-state-point
  (make-primitive-procedure 'TRANSLATE-TO-STATE-POINT))

(define (nearest-state-point space)
  (vector-ref space 1))

;;; The following code implements the current model of DYNAMIC-WIND as
;;; a special case of the more general concept.

(define system-state-space
  (make-state-space))

(define (current-dynamic-state)
  (nearest-state-point system-state-space))

(define (dynamic-wind before during after)
  (execute-at-new-state-point system-state-space
			      before
			      after
			      during))