59 lines
2.5 KiB
Racket
59 lines
2.5 KiB
Racket
#lang racket/base
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(require (for-syntax racket/base
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compiler/cm-accomplice)
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racket/runtime-path
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racket/promise)
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(provide lazy-require)
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(define-syntax (lazy-require stx)
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(syntax-case stx ()
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[(lazy-require [modpath (thing ...)] ...)
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#`(begin (define-namespace-anchor anchor)
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(lazy-require1 modpath (thing ...) anchor #,stx)
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...)]))
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(define-syntax (lazy-require1 stx)
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(syntax-case stx ()
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[(lazy-require1 modpath (name ...) anchor orig-stx)
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(with-syntax ([(defn ...)
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(for/list ([name (in-list (syntax->list #'(name ...)))])
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(unless (identifier? name)
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(raise-syntax-error #f "expected identifier" #'orig-stx name))
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(with-syntax ([name name]
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[(aux) (generate-temporaries (list name))])
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#`(begin (define aux (make-lazy-function 'name get-sym))
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(define-syntax name
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(make-rename-transformer
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(syntax-property (quote-syntax aux)
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'not-provide-all-defined #t))))))])
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;; implicit quasiquote, so can use normal module-path syntax
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;; or escape to compute a the module-path via expression
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#'(begin (define-runtime-module-path-index mpi-var (quasiquote modpath))
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(define-values ()
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(let-syntax ([_ (do-registration (#%variable-reference) (quasiquote modpath))])
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(values)))
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(define (get-sym sym)
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(parameterize ((current-namespace (namespace-anchor->namespace anchor)))
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(dynamic-require mpi-var sym)))
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defn ...))]))
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(define (make-lazy-function name get-sym)
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;; Use 'delay/sync' because 'delay' promise is not reentrant.
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;; FIXME: OTOH, 'delay/sync' promise is not kill-safe.
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(let ([fun-p (delay/sync (get-sym name))])
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(procedure-rename
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(make-keyword-procedure
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(lambda (kws kwargs . args)
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(keyword-apply (force fun-p) kws kwargs args)))
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name)))
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(begin-for-syntax
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(define (do-registration vr modpath)
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(let ([path (resolved-module-path-name
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(module-path-index-resolve
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(module-path-index-join
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modpath
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(variable-reference->resolved-module-path vr))))])
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(when (path? path)
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(register-external-file path)))))
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