Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 01:15:28 UTC, Dan wrote: I've seen these type of errors often and usually the cause kind of jumps out. In this case I'm totally confused. Just trying to move from 2.06 to 2.061. The code is: http://dpaste.dzfl.pl/f40e4d6f and fails with the error in subject line. Observations: - If static if(1) is changed to static if(0) it compiles - If either _valuationHistory or goo member of BSItem is commented out it compiles. I know the code is somewhat cryptic, but I've been using binary reduction comment in/out to try to narrow down this issue. I can not understand why an introduction of opEquals on a struct History with no relationship to RC causes an error to show for RC. Thanks Dan There is still problem with const structs vs. non-const postblit and destructor. In the past, the situation was even worse, but was partly fixed by laxing constness with respect to postblit and destructor. Now all such problems seems to come from associative array implementation in object.d
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 04:03:06 UTC, Andrej Mitrovic wrote: Yeah, it's still not very helpful. And I have no idea where Slot comes from. This is sub struct inside object.AssociativeArray.
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 11:51:40 UTC, Maxim Fomin wrote:
On Tuesday, 5 February 2013 at 04:03:06 UTC, Andrej Mitrovic
wrote:
Yeah, it's still not very helpful. And I have no idea where
Slot comes from.
This is sub struct inside object.AssociativeArray.
Is it the case that this is a D compiler (or library) problem and
there is no issue with the code? Or is there really a problem
with it that I am not seeing? I gather from the responses the
code looks fine, otherwise any misunderstanding would come up
quickly.
I feel like I have painted myself in a corner a bit. I love D's
templates and am a fan of the compile time reflection. I have
mixins that support things like OpEquals, OpCmp, toHash, etc. I
try very hard to work with const correctly.
mixin template OpEquals() {
bool opEquals(const ref typeof(this) other) const {
return typesDeepEqual(this, other);
}
bool opEquals(const typeof(this) other) const {
return typesDeepEqual(this, other);
}
}
This OpEquals in the sample was just this signature (which I have
mixed in all over successfully) but with a 'return true'. I think
this is the correct signature to use. If I understand correctly,
were I to remove the const, then const instances may no longer
call it - which is not a good change.
Transitive const is more than just simple const, and obviously
more is better ;-). Since Slot is mentioned and
object.AssociativeArrray it sounds like there may be a
const-correctness issue with associative array itself rather than
this code? Before the move to 2.061 I had to cast away const on
const(V[K]) to get length and to iterate over them. But why the
link between History!double and RC[int] when they are totally
unrelated? Well, the only relation is their aggregation in
BSItem. Baffling.
Any suggestions appreciated.
Thanks
Dan
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 15:06:47 UTC, Maxim Fomin wrote:
The root of the problem is in:
struct DAssociativeArray(Key, Value)
{
struct Slot
{
Value value;
}
}
struct RC {
this(this) { }
}
void main()
{
DAssociativeArray!(int, const(RC)) goo;
}
which doesn't compile (this is how Value[Key] is rewritten).
I see - thanks. I assume it should compile and without the
postblit it does. So - the original code is fine and there is a D
problem with associative arrays.
- Wouldn't the scenario be exactly the same without
ValuationHistory? That is, if I comment out the member
_valuationHistory, the goo member is not changed in structure at
all, and yet it compiles just fine.
- Does this mean that no one or very few developers store
structs with postblits as value types in the standard associative
array? Maybe I just do things differently than others.
The way I see it you have to choose how you want to develop your
structs/classes. I have chosen to use structs and templates and
avoid classes, thinking this would greatly simplify things. Any
struct needs to establish up front whether it will have value
semantics or reference semantics. So far, I have preferred value
semantics as data sharing leads to confusion. So if I have arrays
in a struct I include postblits to provide value semantics. In
another thread Walter made clear his distaste for postblits and
preference for reference semantics coupled with copy on write
semantics where needed. That approach, just does not seem worth
it without more systematic support for COW. Assuming postblits
are the issue, I don't understand why they are so hard to get
right.
Thanks
Dan
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 15:49:59 UTC, Dan wrote:
- Wouldn't the scenario be exactly the same without
ValuationHistory? That is, if I comment out the member
_valuationHistory, the goo member is not changed in structure
at all, and yet it compiles just fine.
Scenario is the same if there is struct with postblit and
const(S) is passed as AA argument. If there is more code
involved, the situation can be more complicated.
- Does this mean that no one or very few developers store
structs with postblits as value types in the standard
associative array? Maybe I just do things differently than
others.
This does not imply such situation, simply there is a problem.
You can workaround by
struct DAssociativeArray(Key, Value)
{
struct Slot
{
Value value;
}
}
struct RC {
int i;
void postblit() { i = -5; }
this(this) const
{
void delegate() dg = postblit;
dg();
}
}
void main()
{
RC rc1 = RC(5);
RC rc2 = rc1;
assert(rc2.i is -5);
DAssociativeArray!(int, const(RC)) goo;
}
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 16:36:16 UTC, Maxim Fomin wrote:
This does not imply such situation, simply there is a problem.
You can workaround by
[snip]
struct RC {
int i;
void postblit() { i = -5; }
this(this) const
{
void delegate() dg = postblit;
dg();
}
}
Great thanks. I'll try.
But why does this even code work? I would have thought const
guarantee would prevent calls to non-const postblit function. I
was under impression this(this) const does not work - but maybe
that has changed with 2.061.
What source (lang spec, TDPL, or newsgroup) led you to this
solution and for how long will it be valid? Where can I read more
on it?
Thanks
Dan
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 17:05:23 UTC, Dan wrote: But why does this even code work? I would have thought const guarantee would prevent calls to non-const postblit function. I was under impression this(this) const does not work - but maybe that has changed with 2.061. Forgot to mention, it works on 2.061. What source (lang spec, TDPL, or newsgroup) led you to this solution and for how long will it be valid? Where can I read more on it? Thanks Dan Const postblit worked at least at 2.060. Originally idea was to make const cast on function call, but at a current time it is not needed. May be another bug.
x.RC.__postblit () is not callable using argument types () const
I've seen these type of errors often and usually the cause kind of jumps out. In this case I'm totally confused. Just trying to move from 2.06 to 2.061. The code is: http://dpaste.dzfl.pl/f40e4d6f and fails with the error in subject line. Observations: - If static if(1) is changed to static if(0) it compiles - If either _valuationHistory or goo member of BSItem is commented out it compiles. I know the code is somewhat cryptic, but I've been using binary reduction comment in/out to try to narrow down this issue. I can not understand why an introduction of opEquals on a struct History with no relationship to RC causes an error to show for RC. Thanks Dan
Re: x.RC.__postblit () is not callable using argument types () const
On 02/04/2013 05:15 PM, Dan wrote:
I've seen these type of errors often and usually the cause kind of jumps
out. In this case I'm totally confused. Just trying to move from 2.06 to
2.061.
The code is: http://dpaste.dzfl.pl/f40e4d6f
and fails with the error in subject line. Observations:
- If static if(1) is changed to static if(0) it compiles
- If either _valuationHistory or goo member of BSItem is commented out
it compiles.
I know the code is somewhat cryptic, but I've been using binary
reduction comment in/out to try to narrow down this issue. I can not
understand why an introduction of opEquals on a struct History with no
relationship to RC causes an error to show for RC.
Thanks
Dan
Further reduced:
struct History(V) {
bool opEquals(const typeof(this) other) const {
return true;
}
}
struct RC {
this(this) { _impl = _impl.dup; }
string[] _impl;
}
struct BSItem {
ValuationHistory _valuationHistory;
RC[int] goo;
}
struct ValuationHistory {
History!double _history;
}
void main() {
}
The problem is related to History.opEquals being 'const'. Remove that
'const' and the code compiles. This must be a (lack of)
const-correctness issue.
Ali
Re: x.RC.__postblit () is not callable using argument types () const
On Tuesday, 5 February 2013 at 01:38:54 UTC, Ali Çehreli wrote: Further reduced: [snip] The problem is related to History.opEquals being 'const'. Remove that 'const' and the code compiles. This must be a (lack of) const-correctness issue. Thanks Ali. If const is removed it will compile. I think you are correct it is a const issue, but I'm at a loss as to why? After all, it does not access anything and just returns true. I don't see any const issues. I can't say for sure, but I feel this worked fine in 2.06. What I find troubling is how long it took me cull the code to the offending and I still don't understand the error. Thanks Dan
Re: x.RC.__postblit () is not callable using argument types () const
On 2/5/13, Dan dbdavid...@yahoo.com wrote: and I still don't understand the error. The error in the git-head version is: Error: mutable method test.RC.__postblit is not callable using a const object Error: cannot modify struct this Slot with immutable members Yeah, it's still not very helpful. And I have no idea where Slot comes from.
