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(define-module (language python with)
#:use-module (language python try)
#:use-module (language python exceptions)
#:use-module (oop pf-objects)
#:export (with))
(define-syntax-rule (aif it p x y) (let ((it p)) (if it x y)))
(define-syntax with
(syntax-rules ()
((_ () . code)
(begin . code))
((_ (x . l) . code)
(with0 x (with l . code)))))
(define-syntax with0
(syntax-rules ()
((_ (id exp) . code)
(let ((type None)
(value None)
(trace None))
(aif exit (ref exp '__exit__)
(aif enter (ref exp '__enter__)
(try
(lambda ()
(let ((id (enter))) . code))
(#:except #t =>
(lambda (tag l)
(set! type (if (pyclass? tag)
tag
(aif it (ref tag '__class__)
it
tag)))
(set! value
(aif it (ref tag 'value)
it
(if (pair? l)
(car l)
None)))))
#:finally
(lambda ()
(exit type value trace)))
(raise TypeError "no __enter__ member"))
(raise TypeError "no __exit__ member"))))
((_ (exp) . code)
(with0 (id exp) . code))))
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