On Mar 5, 2007, at 12:47 PM, Bradley Lucier wrote:
On Mar 5, 2007, at 10:36 AM, William D Clinger wrote:
Brad Lucier wrote:
I presume that many people might want to use bytevectors as
described
in this report to increase computational speed and decrease memory
requirements by avoiding boxing/unboxing of objects that might
otherwise be boxed when held in generic vectors.
Me too. I have been assuming that someone would write
a SRFI for type-specific numeric vectors together with
a portable R6RS reference implementation using bytevectors
encapsulated within records.
If you or I were to write that SRFI, it would solve the
aliasing problem without even having to mention it.
Will it? The components of two records, one holding ints, one
holding floats (or, here we go, one holding *both* floats and ints,
which is what is really envisaged by this proposal) could not be
the same bytevector?
I haven't looked at the record proposal, so I don't know.
I interpreted the proposal as saying that this hypothetical SRFI
would be specified in a manner that *allows* an implementation to
choose a implementation-specific representation that enforces the
aliasing guarantees you desire. The hypothetical SRFI would also
provide a reference implementation that has observationally
equivalent behavior, but would probably not be able to be similarly
optimized by standard compilation technology.
(I am assuming that the record system proposed in R^{5.92}RS allows
for this sort of encapsulation, but I have not verified this.)
-Felix
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