• deadalnix (8/8) Feb 21 2012 struct stuff {
• Vladimir Panteleev (7/17) Feb 21 2012 Delegates contain a context pointer. Your delegate literal has no
• deadalnix (5/21) Feb 21 2012 It doesn't work with function either.
• Vladimir Panteleev (9/40) Feb 21 2012 struct stuff {
• deadalnix (3/38) Feb 22 2012 This look very promizing !!!
• H. S. Teoh (8/21) Feb 22 2012 But doesn't this only work for function pointers? I don't think you can
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (4/28) Feb 22 2012 Could std.functional.toDelegate be helpful here?
• Adam D. Ruppe (2/2) Feb 21 2012 A possible workaround is to initialize the delegate
• deadalnix (3/5) Feb 21 2012 It is a struct. And struct don't have default constructor. It lead to
• Jacob Carlborg (4/9) Feb 21 2012 You can implement a static opCall and use that instead of the constructo...
• deadalnix (2/10) Feb 22 2012 It's a cheap replacement because it doesn't allow to new.
• Stewart Gordon (6/8) Feb 25 2012 But you don't have to call a static opCall. You can just declare a stru...
• Timon Gehr (6/15) Feb 25 2012 struct exceptionBuilder{
• Artur Skawina (9/27) Feb 25 2012 Too bad this doesn't work when opCall takes args.
• Timon Gehr (3/30) Feb 25 2012 Well, that is a bug.
• Mantis (12/20) Feb 21 2012 The compiler expects member initializers to be known at compile-time.
• deadalnix (5/28) Feb 21 2012 I think this the best solution after all.
• H. S. Teoh (6/9) Feb 21 2012 You could file an enhancement request, if one hasn't already been filed.
• Timon Gehr (2/10) Feb 22 2012 Bug or not, It is an annoying limitation.

deadalnix <deadalnix gmail.com> writes:

struct stuff {
	private Exception delegate() exceptionBuilder = delegate Exception() {
		return new Exception("foobar");
	};
}

The following piece of code trigger a compiler error : delegate 
module.stuff.__dgliteral1 function literals cannot be class members

Why is that ? Is it a bug or a feature ?

"Vladimir Panteleev" <vladimir thecybershadow.net> writes:

On Tuesday, 21 February 2012 at 15:22:15 UTC, deadalnix wrote:
 struct stuff {
 	private Exception delegate() exceptionBuilder = delegate 
 Exception() {
 		return new Exception("foobar");
 	};
 }

 The following piece of code trigger a compiler error : delegate 
 module.stuff.__dgliteral1 function literals cannot be class 
 members

 Why is that ? Is it a bug or a feature ?

Delegates contain a context pointer. Your delegate literal has no 
context.

You can't initialize it with the address of a method, either. For 
struct methods, the context pointer is a pointer to the 
structure. You can't have a .init that contains a pointer to an 
instance. You probably want to use a function literal.

deadalnix <deadalnix gmail.com> writes:

Le 21/02/2012 16:32, Vladimir Panteleev a écrit :
 On Tuesday, 21 February 2012 at 15:22:15 UTC, deadalnix wrote:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

 Delegates contain a context pointer. Your delegate literal has no context.

 You can't initialize it with the address of a method, either. For struct
 methods, the context pointer is a pointer to the structure. You can't
 have a .init that contains a pointer to an instance. You probably want
 to use a function literal.

It doesn't work with function either.

But I need delegate here. The default one doesn't require a context, but 
isn't it possible to pass null as a context, as none is needed ? This 
value can be changer later, and definitively require to be a delegate.

"Vladimir Panteleev" <vladimir thecybershadow.net> writes:

On Tuesday, 21 February 2012 at 15:41:58 UTC, deadalnix wrote:
 Le 21/02/2012 16:32, Vladimir Panteleev a écrit :
 On Tuesday, 21 February 2012 at 15:22:15 UTC, deadalnix wrote:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate 
 Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : 
 delegate
 module.stuff.__dgliteral1 function literals cannot be class 
 members

 Why is that ? Is it a bug or a feature ?

 Delegates contain a context pointer. Your delegate literal has 
 no context.

 You can't initialize it with the address of a method, either. 
 For struct
 methods, the context pointer is a pointer to the structure. 
 You can't
 have a .init that contains a pointer to an instance. You 
 probably want
 to use a function literal.

 It doesn't work with function either.

 But I need delegate here. The default one doesn't require a 
 context, but isn't it possible to pass null as a context, as 
 none is needed ? This value can be changer later, and 
 definitively require to be a delegate.

struct stuff {
	private Exception function() exceptionBuilder =
		&defaultExceptionBuilder;
	
	private static Exception defaultExceptionBuilder() {
		return new Exception("foobar");
	};
}

deadalnix <deadalnix gmail.com> writes:

Le 22/02/2012 03:59, Vladimir Panteleev a écrit :
 On Tuesday, 21 February 2012 at 15:41:58 UTC, deadalnix wrote:
 Le 21/02/2012 16:32, Vladimir Panteleev a écrit :
 On Tuesday, 21 February 2012 at 15:22:15 UTC, deadalnix wrote:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

 Delegates contain a context pointer. Your delegate literal has no
 context.

 You can't initialize it with the address of a method, either. For struct
 methods, the context pointer is a pointer to the structure. You can't
 have a .init that contains a pointer to an instance. You probably want
 to use a function literal.

 It doesn't work with function either.

 But I need delegate here. The default one doesn't require a context,
 but isn't it possible to pass null as a context, as none is needed ?
 This value can be changer later, and definitively require to be a
 delegate.

 struct stuff {
 private Exception function() exceptionBuilder =
 &defaultExceptionBuilder;

 private static Exception defaultExceptionBuilder() {
 return new Exception("foobar");
 };
 }

This look very promizing !!!

I'll investigate in that direction. Thank you very much for the hint.

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Wed, Feb 22, 2012 at 12:42:44PM +0100, deadalnix wrote:
 Le 22/02/2012 03:59, Vladimir Panteleev a écrit :

[...]
struct stuff {
private Exception function() exceptionBuilder =
&defaultExceptionBuilder;

private static Exception defaultExceptionBuilder() {
return new Exception("foobar");
};
}

 
 This look very promizing !!!
 
 I'll investigate in that direction. Thank you very much for the hint.

But doesn't this only work for function pointers? I don't think you can
later assign a *delegate* to exceptionBuilder. They are different types
(delegates need fat pointers, won't fit in a function pointer).


T

-- 
Trying to define yourself is like trying to bite your own teeth. -- Alan Watts

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

On 02/21/2012 07:43 AM, deadalnix wrote:
 Le 21/02/2012 16:32, Vladimir Panteleev a écrit :
 On Tuesday, 21 February 2012 at 15:22:15 UTC, deadalnix wrote:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

 Delegates contain a context pointer. Your delegate literal has no
 context.

 You can't initialize it with the address of a method, either. For struct
 methods, the context pointer is a pointer to the structure. You can't
 have a .init that contains a pointer to an instance. You probably want
 to use a function literal.

 It doesn't work with function either.

 But I need delegate here. The default one doesn't require a context, but
 isn't it possible to pass null as a context, as none is needed ? This
 value can be changer later, and definitively require to be a delegate.

Could std.functional.toDelegate be helpful here?

   http://dlang.org/phobos/std_functional.html#toDelegate

Ali

"Adam D. Ruppe" <destructionator gmail.com> writes:

A possible workaround is to initialize the delegate
in the object's constructor.

deadalnix <deadalnix gmail.com> writes:

Le 21/02/2012 16:48, Adam D. Ruppe a écrit :
 A possible workaround is to initialize the delegate
 in the object's constructor.

It is a struct. And struct don't have default constructor. It lead to 
very segfault prone code (I did try that).

Jacob Carlborg <doob me.com> writes:

On 2012-02-21 16:55, deadalnix wrote:
 Le 21/02/2012 16:48, Adam D. Ruppe a écrit :
 A possible workaround is to initialize the delegate
 in the object's constructor.

 It is a struct. And struct don't have default constructor. It lead to
 very segfault prone code (I did try that).

You can implement a static opCall and use that instead of the constructor.

-- 
/Jacob Carlborg

deadalnix <deadalnix gmail.com> writes:

Le 21/02/2012 18:46, Jacob Carlborg a écrit :
 On 2012-02-21 16:55, deadalnix wrote:
 Le 21/02/2012 16:48, Adam D. Ruppe a écrit :
 A possible workaround is to initialize the delegate
 in the object's constructor.

 It is a struct. And struct don't have default constructor. It lead to
 very segfault prone code (I did try that).

 You can implement a static opCall and use that instead of the constructor.

It's a cheap replacement because it doesn't allow to new.

Stewart Gordon <smjg_1998 yahoo.com> writes:

On 21/02/2012 17:46, Jacob Carlborg wrote:
 On 2012-02-21 16:55, deadalnix wrote:

<snip>
 You can implement a static opCall and use that instead of the constructor.

But you don't have to call a static opCall.  You can just declare a struct
instance 
without any initialisation.  Presumably half the point is to ensure that
exceptionBuilder 
is still initialised in such cases.

Stewart.

Timon Gehr <timon.gehr gmx.ch> writes:

On 02/25/2012 03:32 PM, Stewart Gordon wrote:
 On 21/02/2012 17:46, Jacob Carlborg wrote:
 On 2012-02-21 16:55, deadalnix wrote:

 <snip>
 You can implement a static opCall and use that instead of the
 constructor.

 But you don't have to call a static opCall. You can just declare a
 struct instance without any initialisation. Presumably half the point is
 to ensure that exceptionBuilder is still initialised in such cases.

 Stewart.

struct exceptionBuilder{
      disable this();
      disable enum init=0;
     static exceptionBuilder opCall(...){...}
}

Artur Skawina <art.08.09 gmail.com> writes:

On 02/25/12 15:37, Timon Gehr wrote:
 On 02/25/2012 03:32 PM, Stewart Gordon wrote:
 On 21/02/2012 17:46, Jacob Carlborg wrote:
 On 2012-02-21 16:55, deadalnix wrote:

 <snip>
 You can implement a static opCall and use that instead of the
 constructor.

 But you don't have to call a static opCall. You can just declare a
 struct instance without any initialisation. Presumably half the point is
 to ensure that exceptionBuilder is still initialised in such cases.

 Stewart.

 
 struct exceptionBuilder{
      disable this();
      disable enum init=0;
     static exceptionBuilder opCall(...){...}
 }

Too bad this doesn't work when opCall takes args.

IOW, "S(2)" results in 

 Error: constructor m.S.this () is not callable using argument types (int)
 Error: constructor m.S.this is not callable because it is annotated with
 disable
 Error: expected 0 arguments, not 1 for non-variadic function type ref S()

Removing the disabled 'this()' makes the error go away and the right
opCall() gets called.

artur

Timon Gehr <timon.gehr gmx.ch> writes:

On 02/25/2012 07:23 PM, Artur Skawina wrote:
 On 02/25/12 15:37, Timon Gehr wrote:
 On 02/25/2012 03:32 PM, Stewart Gordon wrote:
 On 21/02/2012 17:46, Jacob Carlborg wrote:
 On 2012-02-21 16:55, deadalnix wrote:

 <snip>
 You can implement a static opCall and use that instead of the
 constructor.

 But you don't have to call a static opCall. You can just declare a
 struct instance without any initialisation. Presumably half the point is
 to ensure that exceptionBuilder is still initialised in such cases.

 Stewart.

 struct exceptionBuilder{
       disable this();
       disable enum init=0;
      static exceptionBuilder opCall(...){...}
 }

 Too bad this doesn't work when opCall takes args.

 IOW, "S(2)" results in

   Error: constructor m.S.this () is not callable using argument types (int)
   Error: constructor m.S.this is not callable because it is annotated with
 disable
   Error: expected 0 arguments, not 1 for non-variadic function type ref S()

 Removing the disabled 'this()' makes the error go away and the right
 opCall() gets called.

 artur

Well, that is a bug.

http://d.puremagic.com/issues/show_bug.cgi?id=6036

Mantis <mail.mantis.88 gmail.com> writes:

21.02.2012 17:24, deadalnix пишет:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate 
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

The compiler expects member initializers to be known at compile-time. 
Since delegate carries closure, and closure is a run-time phenomena, you 
cannot put it there. That's how I understand it, and I might be wrong. 
Anyway, something like this is possible as a workaround:

struct Foo {
private Exception dg() {
if( m_Dg ) return m_Dg();
return new Exception( "foobar" );
}

private Exception delegate() m_Dg = null;
}

deadalnix <deadalnix gmail.com> writes:

Le 21/02/2012 17:30, Mantis a écrit :
 21.02.2012 17:24, deadalnix пишет:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

 The compiler expects member initializers to be known at compile-time.
 Since delegate carries closure, and closure is a run-time phenomena, you
 cannot put it there. That's how I understand it, and I might be wrong.
 Anyway, something like this is possible as a workaround:

 struct Foo {
 private Exception dg() {
 if( m_Dg ) return m_Dg();
 return new Exception( "foobar" );
 }

 private Exception delegate() m_Dg = null;
 }

I think this the best solution after all.

But still I think the original code should be an error only if it use 
data out of the delegate scope. If it doesn't, frame pointer doesn't 
matter and null can be passed.

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Tue, Feb 21, 2012 at 08:01:18PM +0100, deadalnix wrote:
[...]
 But still I think the original code should be an error only if it
 use data out of the delegate scope. If it doesn't, frame pointer
 doesn't matter and null can be passed.

You could file an enhancement request, if one hasn't already been filed.


T

-- 
I'm still trying to find a pun for "punishment"...

Timon Gehr <timon.gehr gmx.ch> writes:

On 02/21/2012 04:24 PM, deadalnix wrote:
 struct stuff {
 private Exception delegate() exceptionBuilder = delegate Exception() {
 return new Exception("foobar");
 };
 }

 The following piece of code trigger a compiler error : delegate
 module.stuff.__dgliteral1 function literals cannot be class members

 Why is that ? Is it a bug or a feature ?

Bug or not, It is an annoying limitation.