digitalmars.D.learn - copying const struct

Jack Applegame (16/16) Oct 14 2013 Why this doesn't compile?

Benjamin Thaut (8/24) Oct 14 2013 Because in D const is transitive. That means if a reference is const the...

Jack Applegame (2/3) Oct 14 2013 Seems strange, because b2.member is const by declaration.

Dicebot (3/7) Oct 14 2013 Strange indeed and smells like a bug. `auto bar =

Benjamin Thaut (2/8) Oct 14 2013 d.puremagic.com/issues/show_bug.cgi?id=9665

Maxim Fomin (2/14) Oct 14 2013 I don't see how this is related to the topic.

Benjamin Thaut (2/14) Oct 14 2013 I thought maybe its related to this bug.

Maxim Fomin (2/18) Oct 14 2013 This is compilable using git head.

Kenji Hara (5/29) Oct 14 2013 Recently I found a small compiler bug.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= (5/8) Oct 14 2013 ... I was thinking about that person. :)

Maxim Fomin (16/24) Oct 14 2013 Right. Kenji is true D celebrity. Funniest thing happen in cases

Jack Applegame (4/8) Oct 14 2013 Obviously Kenji has a time machine. With it, he discovers bugs in

"Jack Applegame" <japplegame gmail.com> writes:

Why this doesn't compile?

http://dpaste.dzfl.pl/21ef5b04

class Foo {}

struct Bar1 {
	const(Foo[]) member;	
}

struct Bar2 {
	const Foo member;	
}

void main() {
	const Bar1 bar1;
	const Bar2 bar2;
	Bar1 b1 = bar1; // ok
	Bar2 b2 = bar2; // cannot implicitly convert expression (bar2) 
of type const(Bar2) to Bar2
}

Oct 14 2013

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 14.10.2013 13:35, schrieb Jack Applegame:
 Why this doesn't compile?

 http://dpaste.dzfl.pl/21ef5b04

 class Foo {}

 struct Bar1 {
      const(Foo[]) member;
 }

 struct Bar2 {
      const Foo member;
 }

 void main() {
      const Bar1 bar1;
      const Bar2 bar2;
      Bar1 b1 = bar1; // ok
      Bar2 b2 = bar2; // cannot implicitly convert expression (bar2) of
 type const(Bar2) to Bar2
 }

Because in D const is transitive. That means if a reference is const the 
object it points to is also const. And everything that object points to 
is const, and so on.

The line "Bar2 b2 = bar2;" would remove const from "member" which does 
not happen because const is not convertible to mutable implicitly.

Kind Regards
Benjamin Thaut

Oct 14 2013

"Jack Applegame" <japplegame gmail.com> writes:

On Monday, 14 October 2013 at 11:38:23 UTC, Benjamin Thaut wrote:
 The line "Bar2 b2 = bar2;" would remove const from "member"

Seems strange, because b2.member is const by declaration.

Oct 14 2013

"Dicebot" <public dicebot.lv> writes:

On Monday, 14 October 2013 at 11:45:30 UTC, Jack Applegame wrote:
 On Monday, 14 October 2013 at 11:38:23 UTC, Benjamin Thaut 
 wrote:
 The line "Bar2 b2 = bar2;" would remove const from "member"

 Seems strange, because b2.member is const by declaration.

Strange indeed and smells like a bug. `auto bar = 
Bar2(bar2.member)` works so it should be assignable.

Oct 14 2013

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 14.10.2013 13:54, schrieb Dicebot:
 On Monday, 14 October 2013 at 11:45:30 UTC, Jack Applegame wrote:
 On Monday, 14 October 2013 at 11:38:23 UTC, Benjamin Thaut wrote:
 The line "Bar2 b2 = bar2;" would remove const from "member"

 Seems strange, because b2.member is const by declaration.

 Strange indeed and smells like a bug. `auto bar = Bar2(bar2.member)`
 works so it should be assignable.

d.puremagic.com/issues/show_bug.cgi?id=9665

Oct 14 2013

"Maxim Fomin" <maxim maxim-fomin.ru> writes:

On Monday, 14 October 2013 at 13:56:58 UTC, Benjamin Thaut wrote:
 Am 14.10.2013 13:54, schrieb Dicebot:
 On Monday, 14 October 2013 at 11:45:30 UTC, Jack Applegame 
 wrote:
 On Monday, 14 October 2013 at 11:38:23 UTC, Benjamin Thaut 
 wrote:
 The line "Bar2 b2 = bar2;" would remove const from "member"

 Seems strange, because b2.member is const by declaration.

 Strange indeed and smells like a bug. `auto bar = 
 Bar2(bar2.member)`
 works so it should be assignable.

 d.puremagic.com/issues/show_bug.cgi?id=9665

I don't see how this is related to the topic.

Oct 14 2013

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 14.10.2013 16:19, schrieb Maxim Fomin:
 On Monday, 14 October 2013 at 13:56:58 UTC, Benjamin Thaut wrote:
 Am 14.10.2013 13:54, schrieb Dicebot:
 On Monday, 14 October 2013 at 11:45:30 UTC, Jack Applegame wrote:
 On Monday, 14 October 2013 at 11:38:23 UTC, Benjamin Thaut wrote:
 The line "Bar2 b2 = bar2;" would remove const from "member"

 Seems strange, because b2.member is const by declaration.

 Strange indeed and smells like a bug. `auto bar = Bar2(bar2.member)`
 works so it should be assignable.

 d.puremagic.com/issues/show_bug.cgi?id=9665

 I don't see how this is related to the topic.

I thought maybe its related to this bug.

Oct 14 2013

"Maxim Fomin" <maxim maxim-fomin.ru> writes:

On Monday, 14 October 2013 at 11:35:32 UTC, Jack Applegame wrote:
 Why this doesn't compile?

 http://dpaste.dzfl.pl/21ef5b04

 class Foo {}

 struct Bar1 {
 	const(Foo[]) member;	
 }

 struct Bar2 {
 	const Foo member;	
 }

 void main() {
 	const Bar1 bar1;
 	const Bar2 bar2;
 	Bar1 b1 = bar1; // ok
 	Bar2 b2 = bar2; // cannot implicitly convert expression (bar2) 
 of type const(Bar2) to Bar2
 }

This is compilable using git head.

Oct 14 2013

"Kenji Hara" <k.hara.pg gmail.com> writes:

On Monday, 14 October 2013 at 14:18:10 UTC, Maxim Fomin wrote:
 On Monday, 14 October 2013 at 11:35:32 UTC, Jack Applegame 
 wrote:
 Why this doesn't compile?

 http://dpaste.dzfl.pl/21ef5b04

 class Foo {}

 struct Bar1 {
 	const(Foo[]) member;	
 }

 struct Bar2 {
 	const Foo member;	
 }

 void main() {
 	const Bar1 bar1;
 	const Bar2 bar2;
 	Bar1 b1 = bar1; // ok
 	Bar2 b2 = bar2; // cannot implicitly convert expression 
 (bar2) of type const(Bar2) to Bar2
 }

 This is compilable using git head.

Recently I found a small compiler bug.
http://d.puremagic.com/issues/show_bug.cgi?id=11187

And, a week ago it is fixed. 2.064 beta1 contains the fix.

Kenji Hara

Oct 14 2013

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 10/14/2013 10:33 AM, Kenji Hara wrote:

 On Monday, 14 October 2013 at 14:18:10 UTC, Maxim Fomin wrote:

 This is compilable using git head.


When I read that line ...

 Kenji Hara

... I was thinking about that person. :)

Thank you Kenji!

Ali

Oct 14 2013

"Maxim Fomin" <maxim maxim-fomin.ru> writes:

On Monday, 14 October 2013 at 17:38:22 UTC, Ali Çehreli wrote:
 On 10/14/2013 10:33 AM, Kenji Hara wrote:

 On Monday, 14 October 2013 at 14:18:10 UTC, Maxim Fomin wrote:

 This is compilable using git head.


 When I read that line ...

 Kenji Hara

 ... I was thinking about that person. :)

 Thank you Kenji!

 Ali

Right. Kenji is true D celebrity. Funniest thing happen in cases 
like this when he reports the bug himself and soon fixes it, 
later bug is hit by someone else but during reporting it is 
realized that bug is already fixed, pull is pushed to master and 
everyone salutes Kenji.

What bothers me is that some (in fact, probably many) delicate 
language cases are silently fixed by Kenji without proper 
documentation so D language has some sparse and obsolete spec, 
even more obsolete book and sporadic patches - just couple of 
developers are aware about each of them. When someone hits corner 
language case - weird compiler behavior it is general unknown 
what should compiler do, whether current behavior is bug or a fix 
for some other previous bug about which you are unaware of. When 
different parts of language interact, problem becomes even more 
complicated.

Oct 14 2013

"Jack Applegame" <japplegame gmail.com> writes:

On Monday, 14 October 2013 at 18:36:00 UTC, Maxim Fomin wrote:
 Funniest thing happen in cases like this when he reports the 
 bug himself and soon fixes it, later bug is hit by someone else 
 but during reporting it is realized that bug is already fixed, 
 pull is pushed to master and everyone salutes Kenji.

Obviously Kenji has a time machine. With it, he discovers bugs in 
the future and fixes them in the present and sometimes even in 
the past.

Oct 14 2013

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digitalmars.D.learn - copying const struct