On Thu, 08 Nov 2012 14:55:21 +0100, Matthew Flatt <mfl...@cs.utah.edu>
wrote:
[ ... ]
It's interesting that you can make that work in the current
implementation, but I worry about guaranteeing that order for the
future. I'm inclined instead to say that the above declaration should
have signaled an error due to an too-early use of `_S', just like
(struct a () #:property prop:procedure struct:a)
The repair to `define-cstruct', then, would be to lift the property and
property-value expressions out of the nested scope where they currently
are evaluated.
Is it important for your purposes that the `define-cstruct' declaration
above works? Or could you use a thunk to delay reference, as in
(define-cstruct _S ([a (_array _byte 23)])
#:property p (lambda () _S))
?
That was a possibility i also tried, but with the same erroneous result.
(define-cstruct _S ([a (_array _byte 23)])
#:property p (lambda () _S))
(define s (ptr-ref (malloc _S) _S))
(ctype-sizeof ((p-ref s)))
4
(ctype-sizeof _S)
23
I assume _S binds to the variable in the scope it is defined in,
which is always the temporary cpointer.
--
---------------------------------------------------------
Tobias Hammer
DLR / Institute of Robotics and Mechatronics
Muenchner Str. 20, D-82234 Wessling
Tel.: 08153/28-1487
Mail: tobias.ham...@dlr.de
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