98 lines
2.9 KiB
Scheme
98 lines
2.9 KiB
Scheme
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; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees. See file COPYING.
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; Accessing packages
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(define (environment-ref package name)
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(carefully (package-lookup package name) contents package name))
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(define (environment-set! package name value)
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(let ((binding (package-lookup package name)))
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(if (and (binding? binding)
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(not (variable-type? (binding-type binding))))
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(error "invalid assignment" name package value)
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(carefully binding
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(lambda (loc)
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(set-contents! loc value))
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package name))))
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(define (environment-define! package name value)
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(set-contents! (package-define! package name usual-variable-type) value))
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(define (*structure-ref struct name)
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(let ((binding (structure-lookup struct name #f)))
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(if binding
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(carefully binding contents struct name)
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(error "structure-ref: name not exported" struct name))))
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(define (carefully binding action env name)
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(if (binding? binding)
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(if (eq? (binding-type binding) syntax-type)
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(error "attempt to reference syntax as variable" name env)
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(let ((loc (binding-place binding)))
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(if (location? loc)
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(if (location-defined? loc)
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(action loc)
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(error "unbound variable" name env))
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(error "variable has no location" name env))))
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(if (unbound? binding)
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(error "unbound variable" name env)
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(error "peculiar binding" binding name env))))
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; Interaction environment
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(define $interaction-environment (make-fluid #f))
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(define (interaction-environment)
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(fluid $interaction-environment))
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(define (set-interaction-environment! p)
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(if (package? p)
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(set-fluid! $interaction-environment p)
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(call-error "invalid package" set-interaction-environment! p)))
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(define (with-interaction-environment p thunk)
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(if (package? p)
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(let-fluid $interaction-environment p thunk)
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(call-error "invalid package" with-interaction-environment p)))
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; Scheme report environment. Should be read-only; fix later.
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(define (scheme-report-environment n)
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(if (= n *scheme-report-number*)
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*scheme-report-environment*
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(error "no such Scheme report environment")))
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(define *scheme-report-environment* #f)
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(define *scheme-report-number* 0)
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(define (set-scheme-report-environment! repnum env)
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(set! *scheme-report-number* repnum)
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(set! *scheme-report-environment* env))
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; Make an infinite tower of packages for syntax.
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; structs should be a non-null list of structures that should be
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; opened at EVERY level of the tower.
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(define (make-reflective-tower eval structs id)
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(let recur ((level 1))
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(delay (cons eval
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(make-simple-package structs
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eval
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(recur (+ level 1))
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`(for-syntax ,level ,id))))))
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; (set-reflective-tower-maker! p (lambda (clauses id) ...))
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; where clauses is a list of DEFINE-STRUCTURE clauses
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(define set-reflective-tower-maker!
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(let ((name (string->symbol ".make-reflective-tower.")))
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(lambda (p proc)
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(environment-define! p name proc))))
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