Re: Encapsulate return value in scoped
On Friday, 19 June 2015 at 00:00:50 UTC, Ali Çehreli wrote: On 06/18/2015 04:53 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 21:38:59 UTC, Ali Çehreli wrote: About returning scoped!C, I think it works: I just find out that the document of scoped says that It's Thanks for fixing the typo there. (The documentations has lower case: it's. ;) ) illegal to move a class instance Wait! You fixed that as well? :) The doc that I am looking at says class reference: http://dlang.org/phobos/std_typecons.html#.scoped Those are fixed by: https://github.com/D-Programming-Language/phobos/pull/3016 even if you are sure there are no pointers to it. As such, it is illegal to move a scoped object. So this is not a solution? I guess not. :-/ Ali I don't understand. What problem can moving a scoped cause when there's no reference to its inner class?
Re: Encapsulate return value in scoped
On 06/18/2015 05:25 PM, Yuxuan Shui wrote: What problem can moving a scoped cause when there's no reference to its inner class? I am curious as well. Could it be related to the object's 'monitor'? Perhaps some other code may have a reference to monitor? And that reference does not constitute as a reference to the object itself? I don't know. Ali
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 21:38:59 UTC, Ali Çehreli wrote:
On 06/11/2015 12:51 PM, Yuxuan Shui wrote:
On Thursday, 11 June 2015 at 19:23:49 UTC, Ali Çehreli wrote:
[...]
Can you explain more about why the destructor is not called
when
returning a struct?
Are you asking in general or specific to scoped!C?
In general, D has move semantics built into the language. It
depends on whether the returned expression is an rvalue or an
lvalue: rvalues are moved, lvalues are copied. And the
destructor will not be called for a moved object.
About returning scoped!C, I think it works:
import std.stdio;
import std.typecons;
class C
{
~this()
{
writeln(dtor);
}
}
auto foo()
{
auto c = scoped!C();
return c;
}
void main()
{
writeln(entering scope);
{
writeln(calling);
auto s = foo();
writeln(returned);
}
writeln(leaving scope);
}
dtor is printed upon leaving the scope:
entering scope
calling
returned
dtor
leaving scope
Ali
I just find out that the document of scoped says that It's
illegal to move a class instance even if you are sure there are
no pointers to it. As such, it is illegal to move a scoped
object.
So this is not a solution?
Re: Encapsulate return value in scoped
On 06/18/2015 04:53 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 21:38:59 UTC, Ali Çehreli wrote: About returning scoped!C, I think it works: I just find out that the document of scoped says that It's Thanks for fixing the typo there. (The documentations has lower case: it's. ;) ) illegal to move a class instance Wait! You fixed that as well? :) The doc that I am looking at says class reference: http://dlang.org/phobos/std_typecons.html#.scoped even if you are sure there are no pointers to it. As such, it is illegal to move a scoped object. So this is not a solution? I guess not. :-/ Ali
Re: Encapsulate return value in scoped
On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10);
Encapsulate return value in scoped
Is there a way to encapsulate return value into scoped?
Say I have a function that returns a new object:
X new_x(T t...) {
//Super complex input processing
return new X(something);
}
And I want to encapsulate the result using scoped, is that
possible? Can I just do:
return scoped!X(something).
?
If I understand correctly, the data will be blitted, but the
destructor will be called, so the returned object will be in
invalid state.
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 08:48:22 UTC, Yuxuan Shui wrote:
Is there a way to encapsulate return value into scoped?
Say I have a function that returns a new object:
X new_x(T t...) {
//Super complex input processing
return new X(something);
}
And I want to encapsulate the result using scoped, is that
possible? Can I just do:
return scoped!X(something).
?
If I understand correctly, the data will be blitted, but the
destructor will be called, so the returned object will be in
invalid state.
It's even weirder than I thought, this:
import std.stdio,
std.typecons;
class A {
int b;
~this() {
writeln(Des);
}
this(int x) {
b=x;
writeln(Cons);
}
}
auto x() {
A x = scoped!A(10);
writeln(x.b);
writeln(Return x);
return x;
}
void main() {
auto tx = x();
writeln(Return main);
}
Produce output:
Cons
Des
0
Return x
Return main
Which I totally don't understand.
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code?
Re: Encapsulate return value in scoped
On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process.
Re: Encapsulate return value in scoped
On 06/11/2015 11:43 AM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process. Shameless plug: :) http://ddili.org/ders/d.en/destroy.html#ix_destroy.scoped This issue is explained at the end of that section. Ali
Re: Encapsulate return value in scoped
On Thursday, 11 June 2015 at 19:23:49 UTC, Ali Çehreli wrote: On 06/11/2015 11:43 AM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 17:34:56 UTC, Steven Schveighoffer wrote: On 6/11/15 1:28 PM, Yuxuan Shui wrote: On Thursday, 11 June 2015 at 09:11:47 UTC, Daniel Kozák wrote: On Thu, 11 Jun 2015 09:01:04 + Yuxuan Shui via Digitalmars-d-learn digitalmars-d-learn@puremagic.com wrote: A x = scoped!A(10); use auto x = scoped!A(10); Thanks! Curious question, why doesn't compiler reject this code? Because scoped!A implicitly casts to A. -Steve Thanks! I just found that out myself. Learned 'alias this' in the process. Shameless plug: :) http://ddili.org/ders/d.en/destroy.html#ix_destroy.scoped This issue is explained at the end of that section. Ali Can you explain more about why the destructor is not called when returning a struct? Can't seem to find it in the document.
