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A lexical use-modules?
From: |
Maxime Devos |
Subject: |
A lexical use-modules? |
Date: |
Sat, 26 Mar 2022 20:21:07 +0100 |
User-agent: |
Evolution 3.38.3-1 |
Hi,
[ CC'ing guix-devel@ because this functionality could be useful in Guix
package definitions ]
Currently, use-modules cannot be meaningfully used inside procedures,
unless '(current-module)' is always the module in which the procedure
is defined.
I wondered if some kind of 'lexical use-modules' was possible, with
sufficient macroology and module reflection, and it looks like it is:
(use-modules (srfi srfi-1))
(define-syntax use-module/lexical
;; todo: integrate into (use-modules ...)?
(lambda (s)
(syntax-case s ()
((_ foo)
(let* ((module-name (syntax->datum #'foo))
(interface (resolve-interface module-name)))
(define (binding->import name variable)
(define name-syntax (datum->syntax s name))
#`(define-syntax #,name-syntax (identifier-syntax (@ foo
#,(datum->syntax #'irrelevant name)))))
#`(begin #,@(module-map binding->import interface)))))))
(define &exception 'top-level)
(let ()
(use-module/lexical (ice-9 exceptions))
(pk 'inner &exception raise-continuable))
;;; (inner #<record-type &exception> #<procedure raise-continuable (obj)>)
(pk 'outer &exception)
;;; (outer top-level)
(pk 'unbound-variable raise-continuable)
;; a backtrace!
Limitation: things like
(define (foo)
(use-module/lexical (platform-specific-constants))
(if on-linux?
CONSTANT_ONLY_DEFINED_ON_LINUX
CONSTANT_ONLY_DEFINED_ON_HURD))
won't work in cross-compilation contexts.
Greetings,
Maxime.
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- A lexical use-modules?,
Maxime Devos <=
Re: A lexical use-modules?, Ludovic Courtès, 2022/03/29
Re: A lexical use-modules?, Maxime Devos, 2022/03/29