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Re: CPS != call/cc
At 8:00 AM -0400 8/7/03, John Clements wrote:
>On Wednesday, August 6, 2003, at 08:01 PM, Dan Sugalski wrote:
>>At 1:10 PM -0400 8/6/03, John Clements wrote:
>>>On Wednesday, August 6, 2003, at 11:00 AM, Peter J. Wasilko, Esq. wrote:
>>>>>Well... it can sort of help, but there are some limits. Multiple
>>>>>stacks tend to solve other problems, and they're certainly useful,
>>>>>but for a CPS scheme you really need more of a linked frame system
>>>>>than a stack system, since the control information really builds up a
>>>>>tree (albeit one often with a single branch) rather than a stack.
>>>> I see, so what would an optimal hardware architecture be for
>>>CPS, or continuation-passing-style, is not the same thing as a
>>>language that includes primitives for continuations.
>>While true, the threads are all in the context of Parrot, so its
>>all semantics and no language. (Well, unless you consider assembly
>>a language, but that's stretching things a bit) The continuations
>>we use as part of the CPS scheme are all first class
>>continuations--the only difference between them and first class
>>continuations you make explicitly is that sometimes you don't have
>>to explicitly make them.
>... and that's a HUGE difference. A difference in expressiveness.
No, actually, it isn't.
>All I'm saying is this: don't give another meaning to the
>well-defined term CPS by using it to refer to any program that
>captures continuations with call/cc or other similar primitives.
>That's not what it means.
I think perhaps you're insufficiently familiar with part of the topic
at hand (parrot) to say that for sure. Parrot *does* use CPS, and the
continuations it uses are, for a variety of reasons, first-class
continuations no different than you'd get if you took a continuation
in a language. (How you got that continuation, via call/cc or
explicit continuation creation, is irrelevant here)
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
firstname.lastname@example.org have teddy bears and even
teddy bears get drunk