Re: maybe-commit fails unconditionally

On Fri, Oct 23, 2009 at 14:13, Roderic Morris <[email protected]> wrote:

> maybe-commit from the low-proposals package seems to always throw an
> exception, claiming that there is no proposal, even when used inside
> e.g. ensure-atomicity.
>
> (current-proposal) => #f
> (ensure-atomicity (current-proposal)) => #(#t #(#f) #(#f) #f)
>
> (maybe-commit) => assertion-violation: no current proposal
> (ensure-atomicity (maybe-commit)) => assertion-violation: no current
> proposal
>
>
> -Roderic
>

maybe-commit clears the current proposal, whether the commit succeeds or
fails:



> (ensure-atomicity (display (maybe-commit)) (display (current-proposal)))
#t#f
assertion-violation: no current proposal [maybe-commit]
> (define p (cons #f #f))
; no values returned
> (ensure-atomicity (provisional-car p) (set-car! p (cons #t #t)) (display
(maybe-commit)) (display (current-proposal)))
#f#f
assertion-violation: no current proposal [maybe-commit]



The assertion-violation is produced by the call to maybe-commit within
call-ensuring-atomicity, the function which ensure-atomicity wraps.