On Thu, 2008-03-13 at 14:19 -0400, Swaroop Sridhar wrote:
> >>> A capture of a by-ref formal variable (x) by an
> >>> inner lambda (L) is safe only if:
> >>>
> >>> (1) L does not escape, or
> >>> (2) The body of L does not use x as an lvalue that is a target of an
> >>> assignment.
Consider::
(define i:(mutable int32) 1))
(define (g x: (by-ref (mutable int32)))
(lambda ()
x)) ;
Note that L escapes but the body of L does not use the captured by-ref
formal parameter as an l-value.
Now consider:
(define captured (g i))
(pair (captured) (begin (set! i (+ i 1)) (captured))
Which must result in (1, 2).
The capture here is actually okay because x is capturing a global, but
that cannot be determined at the point where G is admitted.
So I think that your conditions are not sufficient to ensure safety.
shap
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