/usr/share/racket/pkgs/unstable-lib/lazy-require.rkt is in racket-common 6.1-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | #lang racket/base
(require (for-syntax racket/base)
racket/lazy-require)
(provide lazy-require
begin-on-demand)
#|
begin-on-demand notes/todo
Currently like lazy-require: only supports functions.
The #:export kw is clunky... one might think it would be nice to just
re-use 'provide' syntax. Would get rename, prefix, etc for free. OTOH,
might be misleading: might seem like provide should apply to
*apparent* enclosing module, not module implicitly created by
begin-on-demand.
Another nice idea would be to implement lazy-require in terms of
begin-on-demand and real require. Unfortunately, that would mean we
couldn't have cyclic lazy-requires, which is very useful.
|#
(define-syntax (begin-on-demand stx)
(syntax-case stx ()
[(begin-on-demand #:export (exp ...) body ...)
(with-syntax ([fresh-name (gensym 'on-demand-submodule)])
#'(begin
(module* fresh-name #f
(no-provide body ...)
(check-procedure exp 'exp) ...
(provide exp ...))
(define-namespace-anchor anchor)
(define get-sym
(let ([sub-mpi
(module-path-index-join '(submod "." fresh-name)
(variable-reference->resolved-module-path
(#%variable-reference)))])
(lambda (sym)
(parameterize ((current-namespace (namespace-anchor->namespace anchor)))
(dynamic-require sub-mpi sym)))))
(define exp (make-lazy-function 'exp get-sym)) ...))]))
(define-syntax (no-provide stx)
(syntax-case stx ()
[(_ form)
(let ([eform (local-expand #'form
(syntax-local-context)
#f)])
(syntax-case eform (begin #%provide)
[(begin e ...)
#'(begin (no-provide e) ...)]
[(#%provide . _)
(raise-syntax-error #f "provide not allowed" eform)]
[_ eform]))]
[(_ form ...)
#'(begin (no-provide form) ...)]))
(define (check-procedure x name)
(unless (procedure? x)
(error 'begin-on-demand "name bound on-demand is not a procedure: ~a" name)))
|