On 03/20/2010 07:04 AM, Steven Schveighoffer wrote:
Andrei Alexandrescu Wrote:
[snip]
My response to the above issue is two-pronged:
(a) For List a class would be an alternative
Note, this is impractical if you care about performance (I know,
because originally, dcollections used classes for link nodes).
I agree :o).
(b) To work with pointers to structs use static member functions
and pointers instead of methods and references
This prevents something like a linked list from being used in safe D.
That might be too much of a restriction. Yes, it makes code safer,
but it makes safe D unusable.
Actually, no. Walter's vision is to enable certain pointer uses in
SafeD. Unchecked pointer arithmetic is disabled, but code like the one
below is entirely safe:
List * lst = new List;
List * lst2 = prepend(lst, new List);
In fact, restricting use of ref is beneficial for SafeD because it helps
the static proof that any pointer in SafeD points to the
garbage-collected heap (as opposed to e.g. dangling stack variables).
In an ideal world, if you have your hands on a pointer to a struct,
you should be reasonably certain that that lives on the heap. It
would be just great if D could guarantee that.
again, not in safe D. Anytime pointers enter the mix, safe D is
disqualified, no?
As mentioned above, pointers are still on the table in SafeD. I found
that quite interesting myself :o).
Your idea is good, except I don't see why not make ref scoped ref.
After all ref is currently not an enabler - it could be missing
from the language; pointers are fine. So why not make ref do
something actually interesting?
The whole point was to run an experiment seeing how many things could
be written as scoped ref instead of just ref (leaving ref the way it
is today). If they all can with minor adjustments, then we can
switch scoped ref to simply ref. If some can't, and those also don't
make sense as pointers, then we have a predicament that ref enables
some sort of code that isn't enabled by pointers or scoped ref. My
point was, I don't really know off the top of my head all the cases
for using ref, and you probably don't either. I don't think a
sweeping change like this is good without at least some practical
evidence.
That is very sensible, thanks.
Andrei
