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digitalmars.D - Why type specialization is defined differently than is expression

reply deadalnix <deadalnix gmail.com> writes:
All is in the title.

I can do is(T : class) but not template(T : class) . Is this intended or 
is it because it is ?
Jun 27 2012
parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this intended or
 is it because it is ?


You cannot do is(T : class).
Jun 27 2012
next sibling parent reply =?ISO-8859-1?Q?Alex_R=F8nne_Petersen?= <alex lycus.org> writes:
On 27-06-2012 19:13, Timon Gehr wrote:

 On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this intended or
 is it because it is ?


 You cannot do is(T : class).


I think what's really worrying is that this is legal:

void foo(T : class)()
{
}

But this is not:

template Foo(T : class)
{
}

-- 
Alex Rønne Petersen
alex lycus.org
http://lycus.org
Jun 27 2012
parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 06/27/2012 08:21 PM, Alex Rønne Petersen wrote:

 On 27-06-2012 19:13, Timon Gehr wrote:

 On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this intended or
 is it because it is ?


 You cannot do is(T : class).


 I think what's really worrying is that this is legal:

 void foo(T : class)()
 {
 }


This is not legal.


 But this is not:

 template Foo(T : class)
 {
 }
Jun 27 2012
parent "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 19:23:07 UTC, Timon Gehr wrote:

 This is not legal.


Template type specialization must have a basic type after colon.

s/class/Object

should make it legal. By the way, it is not possible to 
specialize for structs this way, is it? I mean, via template type 
specialization, not via template constraints.
Jun 27 2012
prev sibling parent reply "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 17:13:10 UTC, Timon Gehr wrote:

 On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this 
 intended or
 is it because it is ?


 You cannot do is(T : class).


Why? According to grammar,

IsExpression:
is ( Type : TypeSpecialization )

and

TypeSpecialization:

Type struct union class interface enum function delegate super 
const immutable inout shared return
Jun 27 2012
parent reply "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 20:15:43 UTC, Roman D. Boiko wrote:

 On Wednesday, 27 June 2012 at 17:13:10 UTC, Timon Gehr wrote:

 On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this 
 intended or
 is it because it is ?


 You cannot do is(T : class).


 Why? According to grammar,

 IsExpression:
 is ( Type : TypeSpecialization )

 and

 TypeSpecialization:

 Type struct union class interface enum function delegate super 
 const immutable inout shared return


Sorry, I read like typeof(T):

is(typeof(T):class)
Jun 27 2012
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 27 Jun 2012 16:16:53 -0400, Roman D. Boiko <rb d-coding.com> wrote:


 On Wednesday, 27 June 2012 at 20:15:43 UTC, Roman D. Boiko wrote:

 On Wednesday, 27 June 2012 at 17:13:10 UTC, Timon Gehr wrote:

 On 06/27/2012 03:56 PM, deadalnix wrote:

 All is in the title.

 I can do is(T : class) but not template(T : class) . Is this intended  
 or
 is it because it is ?


 You cannot do is(T : class).


 Why? According to grammar,

 IsExpression:
 is ( Type : TypeSpecialization )

 and




The condition is satisfied if Type is semantically correct and it is the  
same as or can be implicitly converted to TypeSpecialization.  

TypeSpecialization is only allowed to be a Type.<<<






Emphasis added.


 TypeSpecialization:

 Type struct union class interface enum function delegate super const  
 immutable inout shared return




This is only valid for is( Type == TypeSpecialization)

-Steve
Jun 27 2012
parent reply "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 20:27:39 UTC, Steven Schveighoffer 
wrote:

 On Wed, 27 Jun 2012 16:16:53 -0400, Roman D. Boiko 
 <rb d-coding.com> wrote:

 TypeSpecialization:

 Type struct union class interface enum function delegate 
 super const immutable inout shared return




 This is only valid for is( Type == TypeSpecialization)


No, unless the D specification is outdated.

IsExpression:
is ( Type )
is ( Type : TypeSpecialization )
is ( Type == TypeSpecialization )
...
Jun 27 2012
next sibling parent "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 20:32:34 UTC, Roman D. Boiko wrote:

 On Wednesday, 27 June 2012 at 20:27:39 UTC, Steven 
 Schveighoffer wrote:

 On Wed, 27 Jun 2012 16:16:53 -0400, Roman D. Boiko 
 <rb d-coding.com> wrote:

 TypeSpecialization:

 Type struct union class interface enum function delegate 
 super const immutable inout shared return




 This is only valid for is( Type == TypeSpecialization)


 No, unless the D specification is outdated.

 IsExpression:
 is ( Type )
 is ( Type : TypeSpecialization )
 is ( Type == TypeSpecialization )
 ...


Ups... Seems I implemented this incorrectly. Indeed, below there 
is a note:

TypeSpecialization is only allowed to be a Type.
Jun 27 2012
prev sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 27 Jun 2012 16:32:33 -0400, Roman D. Boiko <rb d-coding.com> wrote:


 On Wednesday, 27 June 2012 at 20:27:39 UTC, Steven Schveighoffer wrote:

 On Wed, 27 Jun 2012 16:16:53 -0400, Roman D. Boiko <rb d-coding.com>  
 wrote:

 TypeSpecialization:

 Type struct union class interface enum function delegate super const  
 immutable inout shared return




 This is only valid for is( Type == TypeSpecialization)


 No, unless the D specification is outdated.

 IsExpression:
 is ( Type )
 is ( Type : TypeSpecialization )
 is ( Type == TypeSpecialization )
 ...


It's poorly written, TypeSpecialization is restricted for the : case.   
Maybe it passes the parser, but fails on semantic.

"TypeSpecialization is only allowed to be a Type." -- context for is(Type  
: TypeSpecialization)

-Steve
Jun 27 2012
next sibling parent reply "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 20:35:47 UTC, Steven Schveighoffer 
wrote:

 On Wed, 27 Jun 2012 16:32:33 -0400, Roman D. Boiko 
 <rb d-coding.com> wrote:

 It's poorly written, TypeSpecialization is restricted for the : 
 case.  Maybe it passes the parser, but fails on semantic.

 "TypeSpecialization is only allowed to be a Type." -- context 
 for is(Type : TypeSpecialization)


Yeah, I found that after your post. Probably it was easier to 
implement an IsExpression in a unified way and check semantics 
separately. Otherwise it would be that IsExpression have to 
contain different types of members, if Type (not 
TypeSpecialization) in the `:` case, and the latter in the 
`TypeSpecialization` case.
Jun 27 2012
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 27 Jun 2012 16:40:47 -0400, Roman D. Boiko <rb d-coding.com> wrote:


 On Wednesday, 27 June 2012 at 20:35:47 UTC, Steven Schveighoffer wrote:

 On Wed, 27 Jun 2012 16:32:33 -0400, Roman D. Boiko <rb d-coding.com>  
 wrote:

 It's poorly written, TypeSpecialization is restricted for the : case.   
 Maybe it passes the parser, but fails on semantic.

 "TypeSpecialization is only allowed to be a Type." -- context for  
 is(Type : TypeSpecialization)


 Yeah, I found that after your post. Probably it was easier to implement  
 an IsExpression in a unified way and check semantics separately.  
 Otherwise it would be that IsExpression have to contain different types  
 of members, if Type (not TypeSpecialization) in the `:` case, and the  
 latter in the `TypeSpecialization` case.


Hm... come to think of it, shouldn't TypeSpecialization be Type instead?

Seems weird to say Type : TypeSpecialization, and then say  
"TypeSpecialization is only allowed to be Type".  Why not Type : Type?

-Steve
Jun 27 2012
parent "Roman D. Boiko" <rb d-coding.com> writes:
On Wednesday, 27 June 2012 at 20:42:39 UTC, Steven Schveighoffer 
wrote:

 Hm... come to think of it, shouldn't TypeSpecialization be Type 
 instead?

 Seems weird to say Type : TypeSpecialization, and then say 
 "TypeSpecialization is only allowed to be Type".  Why not Type 
 : Type?


That's what I was trying to explain. It is probably easier to 
implement an IsExpression this way, because it would always 
contain members of the same types.

Also, I made a typo, should be:


 and TypeSpecialization in the `==` case.
Jun 27 2012
prev sibling parent deadalnix <deadalnix gmail.com> writes:
Le 27/06/2012 22:35, Steven Schveighoffer a écrit :

 On Wed, 27 Jun 2012 16:32:33 -0400, Roman D. Boiko <rb d-coding.com> wrote:


 On Wednesday, 27 June 2012 at 20:27:39 UTC, Steven Schveighoffer wrote:

 On Wed, 27 Jun 2012 16:16:53 -0400, Roman D. Boiko <rb d-coding.com>
 wrote:

 TypeSpecialization:

 Type struct union class interface enum function delegate super
 const immutable inout shared return




 This is only valid for is( Type == TypeSpecialization)


 No, unless the D specification is outdated.

 IsExpression:
 is ( Type )
 is ( Type : TypeSpecialization )
 is ( Type == TypeSpecialization )
 ...


 It's poorly written, TypeSpecialization is restricted for the : case.
 Maybe it passes the parser, but fails on semantic.

 "TypeSpecialization is only allowed to be a Type." -- context for
 is(Type : TypeSpecialization)

 -Steve


OK, I had misunderstood here too.

This whole is stuff is kind of messed up.
Jun 27 2012