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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
; Bindings: used to store bindings in packages.
; Representation is #(type place operator-or-transform-or-#f [path]).
; PLACE is a unique (to EQ?) value, usually a location.
; Why aren't these records? Because they need to be written out in
; the initial image?
(define binding? vector?)
(define (binding-type b) (vector-ref b 0))
(define (binding-place b) (vector-ref b 1))
(define (binding-static b) (vector-ref b 2))
(define (binding-path binding)
(if (= 4 (vector-length binding))
(vector-ref binding 3)
#f))
(define (set-binding-place! binding place)
(vector-set! binding 1 place))
(define (make-binding type place static)
(vector type place static))
(define (add-path binding path)
(vector (binding-type binding)
(binding-place binding)
(binding-static binding)
path))
; Used when updating a package binding.
(define (clobber-binding! binding type place static)
(vector-set! binding 0 type)
(if place
(vector-set! binding 1 place))
(vector-set! binding 2 static))
; Return a binding that's similar to the given one, but has its type
; replaced with the given type.
(define (impose-type type binding integrate?)
(if (or (eq? type syntax-type)
(not (binding? binding)))
binding
(make-binding (if (eq? type undeclared-type)
(let ((type (binding-type binding)))
(if (variable-type? type)
(variable-value-type type)
type))
type)
(binding-place binding)
(if integrate?
(binding-static binding)
#f))))
; Return a binding that's similar to the given one, but has any
; procedure integration or other unnecesary static information
; removed. But don't remove static information for macros (or
; structures, interfaces, etc.)
(define (forget-integration binding)
(if (and (binding-static binding)
(subtype? (binding-type binding) any-values-type))
(make-binding (binding-type binding)
(binding-place binding)
#f)
binding))
; Do X and Y denote the same thing?
(define (same-denotation? x y)
(or (eq? x y) ; was EQUAL? because of names, now just for nodes
(and (binding? x)
(binding? y)
(eq? (binding-place x)
(binding-place y)))))
; Special kludge for shadowing and package mutation.
; Ignore this on first reading. See env/shadow.scm.
(define (maybe-fix-place! binding)
(let ((place (binding-place binding)))
(if (and (location? place)
(vector? (location-id place)))
(set-binding-place! binding (follow-forwarding-pointers place))))
binding)
(define (follow-forwarding-pointers place)
(let ((id (location-id place)))
(if (vector? id)
(follow-forwarding-pointers (vector-ref id 0))
place)))
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