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digitalmars.D - Eponymous Aggregates

reply "JS" <js.mdnq gmail.com> writes:
e.g.,

interface A
{
     static T A(T)() { ... }
}

can be used as A!T instead of A.A!T. Same for classes and 
structs. If you want a use case I'm not going to stop you from 
coming up with one... so feel free.
Aug 10 2013
next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
On 8/10/13, JS <js.mdnq gmail.com> wrote:

 e.g.,

 interface A
 {
      static T A(T)() { ... }
 }

 can be used as A!T instead of A.A!T. Same for classes and
 structs.


interface A(T)
{
}
Aug 10 2013
prev sibling parent reply "Simen Kjaeraas" <simen.kjaras gmail.com> writes:
On 2013-08-10, 14:58, JS wrote:


 e.g.,

 interface A
 {
      static T A(T)() { ... }
 }

 can be used as A!T instead of A.A!T. Same for classes and structs. If  
 you want a use case I'm not going to stop you from coming up with one...  
 so feel free.


Tried with DMD 2.063.2, and I'm unable to make A!T compile. Are you sure
you've written the code you intended to?

For reference, this is the code I tried:

interface A {
     static T A(T)() {
         return T.init;
     }
}

void main() {
     A!int a;        // Error: template instance A!(int) A is not a  
template declaration, it is a interface
     auto b = A!int; // Error: template instance A!(int) A is not a  
template declaration, it is a interface
}

This code, of course, works:

template A(T) {
     interface A {
     }
}

void main() {
     A!int a;
}
Aug 10 2013
parent reply "JS" <js.mdnq gmail.com> writes:
On Saturday, 10 August 2013 at 18:28:41 UTC, Simen Kjaeraas wrote:

 On 2013-08-10, 14:58, JS wrote:


 e.g.,

 interface A
 {
     static T A(T)() { ... }
 }

 can be used as A!T instead of A.A!T. Same for classes and 
 structs. If you want a use case I'm not going to stop you from 
 coming up with one... so feel free.


 Tried with DMD 2.063.2, and I'm unable to make A!T compile. Are 
 you sure
 you've written the code you intended to?

 For reference, this is the code I tried:

 interface A {
     static T A(T)() {
         return T.init;
     }
 }

 void main() {
     A!int a;        // Error: template instance A!(int) A is 
 not a template declaration, it is a interface
     auto b = A!int; // Error: template instance A!(int) A is 
 not a template declaration, it is a interface
 }

 This code, of course, works:

 template A(T) {
     interface A {
     }
 }

 void main() {
     A!int a;
 }


No, the code does not compile as it is a proposal.

The issue is simple to allow interfaces to have Eponymous static 
members. This makes it easier to use in some cases. Your template 
example just creates a template... but does nothing as far as 
inheritance.


interface iFactory(A)
{
     static A iFactory(Args...)(Args args) { return new A; }
     // ....
}

class Q : iFactory!Q
{
    // ....
}

auto q = iFactory!Q();

instead of

auto q = iFactory!Q.iFactory();

or

auto q = Q.iFactory()

The last case being only acceptable if Q inherits from 
iFactory(which it may not).

This is simply generalizing eponymous templates to interfaces, 
classes, structs, etc.
Aug 10 2013
parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 08/10/2013 10:10 PM, JS wrote:

 ...
 This is simply generalizing eponymous templates to interfaces, classes,
 structs, etc.


http://i.imgur.com/u29r8pH.jpg
Aug 10 2013
parent "JS" <js.mdnq gmail.com> writes:
On Saturday, 10 August 2013 at 22:17:11 UTC, Timon Gehr wrote:

 On 08/10/2013 10:10 PM, JS wrote:

 ...
 This is simply generalizing eponymous templates to interfaces, 
 classes,
 structs, etc.


 http://i.imgur.com/u29r8pH.jpg


Too bad for you... I already did a few days ago!
Aug 10 2013