Leo~
On Tue, 16 Nov 2004 16:37:04 +0100, Leopold Toetsch <[EMAIL PROTECTED]> wrote:
Matt Fowles <[EMAIL PROTECTED]> wrote: > Leo~
> On Tue, 16 Nov 2004 09:23:24 +0100, Leopold Toetsch <[EMAIL PROTECTED]> wrote:
>> i = 0 >> lp: >> foo() >> inc i >> if i < 10 goto lp
> There is one thing I am not sure about here. The loop will work > correctly for each seperate invocation of the appropriate > continuation.
No. Imagine, foo() is not a simple function anymore. Someone e.g. Jens Rieks[1], discovers that the algoritm is simpler implemented with continuations. So inside foo() the return continuation of foo() is copyied, stored elsewhere, passed along to another function, and that one now suddenly returns via this continuation to your loop. If this invocation of the continuation would restore registers suddenly the loop will become an infinite one, as C<i> is always restored to zero.
[1] Have a look at runtime/parrot/library/Streams/Sub.imc
leo
I disagree with that analysis.
You would, however, in this case be incorrect.
The loop variable must have a backing store outside of the register set. The contents of registers must be assumed to be unreliable when a continuation is continued. If we declare that they are put back into the state they were when the continuation was taken, which is reasonable though not required, the values of non-reference type registers (ints and floats) will be reset. The rference type registers (strings and PMCs) will also be reset so the pointers to the string/pmc structs will be what they were when the continuation was taken, but as they are references the referred-to thing may have changed and the changed value will be seen.
--
Dan
--------------------------------------it's like this-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
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