Thomas Lord wrote:
How would you reconcile your category of "reasonable implementation"
with all of the complexity-varying, all useful approaches to implementing
string-ref that people talk about?
Isn't this part of why strings is so controversial. Different people
want to implement them in different ways and at the same time be able to
access parts of them in a efficient way.
Yes, some of that language probably needs cleaned-up, with particular
attention
to the "must v. should" distinction. My gosh, if we were to get to
that point
before the end of this year, in my view, it'll probably be evidence
that R6 is
shaping up nicely.
It would make it harder to use Scheme as a way to talk about algorithms
and their efficiency if we cannot do some basic assumptions about the
underlying Scheme implementation. Of course one could always say things
like: "On a reasonable implementation this algorithm would be O(n)".
It may be handy to think about observables. In some sense, the meaning
of a program is how it modulates its output ports and responds to
modulations
of its input ports. There are some temporal constraints that relate
those
but mostly in the sense of modeling causality, not performance. It's
useful
to talk about atemporal mathematical objects that relate those
modulations
and that's the level of description I'd expect from a formal
semantics. Formal
operational models, of which it appears their can be many useful ones
with
critical differences among them, are interesting when we can see that
they
in fact satisfy the formal semantic constraints.
It is also interesting to watch how the user alters the semantics of a
program by terminating it prematurely when it fails to respond to user
interaction.
/Mikael
_______________________________________________
r6rs-discuss mailing list
[email protected]
http://lists.r6rs.org/cgi-bin/mailman/listinfo/r6rs-discuss
