dsimcha wrote:
== Quote from Andrei Alexandrescu (seewebsiteforem...@erdani.org)'s article
Walter and I have been discussing what the regime of statically-sized
arrays should be. In short, the behavior that's most consistent with
everything else is to treat them as values.
This also brings the problems of e.g. containers - should they have
consistent value semantics (like in STL)
Oh God no! I always thought the value semantics of STL containers were largely
a
kludge to work around the fact that C++ doesn't have garbage collection. They
make it easier to use RAII for memory management, since every object has a clear
owner. This leads to tons and tons of copying if code is written the obvious
way,
and lots of kludges to prevent it.
Well I never seemed to have a problem with it, quite the contrary in
fact. Values are easier to reason about because they don't have aliasing
and don't foster long-distance interdependencies.
or consistent reference
semantics (like in Java)?
Yes. Largely to be consistent with builtin dynamic arrays and AAs, and for
efficiency, to avoid hidden copying.
Today's dynamic arrays and AAs are really ranges. This becomes most (and
most embarrassingly) visible when expanding a dynamic array with ~=
comes into discussion.
I consider the builtin static arrays to be
just a niche performance hack anyhow, and hardly ever use them because they're
too
inflexible, so consistency with them isn't as important. If you want to
duplicate
something before passing it to something else, attaching a simple .dup to the
end
as in foo(myArray.dup) works pretty darn well. All the standard containers
should
simply have a .dup method, which works similarly to the builtin dynamic array
.dup
method.
Attaching a .dup doesn't always work that pretty darn well because
sometimes you really want .deepdup without realizing it. The .dup
thingie copies only one layer of the onion. To bring this more into
perspective, threading with STM does necessitate guarantees of full,
alias-free copies of entire graphs of objects.
So I guess I disagree with most of your post :o).
Andrei
