• JS (3/3) Jul 13 2013 I need to conditionally inherit:
• JS (4/4) Jul 13 2013 and while I'm at it I need to conditionally constrain types.
• lomereiter (2/6) Jul 13 2013 interface A(T) if (isBasicType!T || is(T : B))
• JS (3/11) Jul 13 2013 Thanks, works. I remember seeing code like this somewhere but
• Simen Kjaeraas (6/17) Jul 14 2013 Here. I admit there should probably be more examples, and perhaps also
• JS (2/20) Jul 14 2013 thanks.
• lomereiter (7/7) Jul 13 2013 This should work:
• JS (6/13) Jul 13 2013 Thanks, I tried something similar but it didn't work right...
• lomereiter (2/4) Jul 14 2013 Yes, it does. Once ':' is typed, some inheritance must occur.
• Timon Gehr (9/13) Jul 14 2013 Nope.
• lomereiter (2/2) Jul 14 2013 Thanks.
• Simen Kjaeraas (12/15) Jul 14 2013 template conditionallyInherit(bool choice, T...) {

"JS" <js.mdnq gmail.com> writes:

I need to conditionally inherit:

interface A(T) : conditionallyInherit!(isBasicType!T, B);

A!(double) will inherit B but A!(mytype) won't.

"JS" <js.mdnq gmail.com> writes:

and while I'm at it I need to conditionally constrain types.

interface A(T) where(!isBasicType!T, (T : B));

which is suppose to require T to inherit from B if T is not basic 
type.

"lomereiter" <lomereiter gmail.com> writes:

On Sunday, 14 July 2013 at 05:04:37 UTC, JS wrote:
 and while I'm at it I need to conditionally constrain types.

 interface A(T) where(!isBasicType!T, (T : B));

 which is suppose to require T to inherit from B if T is not 
 basic type.

interface A(T) if (isBasicType!T || is(T : B))

"JS" <js.mdnq gmail.com> writes:

On Sunday, 14 July 2013 at 05:30:57 UTC, lomereiter wrote:
 On Sunday, 14 July 2013 at 05:04:37 UTC, JS wrote:
 and while I'm at it I need to conditionally constrain types.

 interface A(T) where(!isBasicType!T, (T : B));

 which is suppose to require T to inherit from B if T is not 
 basic type.

 interface A(T) if (isBasicType!T || is(T : B))

Thanks, works. I remember seeing code like this somewhere but 
couldn't find any docs about it.

"Simen Kjaeraas" <simen.kjaras gmail.com> writes:

On 2013-07-14, 07:40, JS wrote:

 On Sunday, 14 July 2013 at 05:30:57 UTC, lomereiter wrote:
 On Sunday, 14 July 2013 at 05:04:37 UTC, JS wrote:
 and while I'm at it I need to conditionally constrain types.

 interface A(T) where(!isBasicType!T, (T : B));

 which is suppose to require T to inherit from B if T is not basic type.

 interface A(T) if (isBasicType!T || is(T : B))

 Thanks, works. I remember seeing code like this somewhere but couldn't  
 find any docs about it.

Here. I admit there should probably be more examples, and perhaps also
some info on the classes/interfaces/structs & unions pages.

http://dlang.org/template.html#Constraint

-- 
Simen

"JS" <js.mdnq gmail.com> writes:

On Sunday, 14 July 2013 at 09:52:29 UTC, Simen Kjaeraas wrote:
 On 2013-07-14, 07:40, JS wrote:

 On Sunday, 14 July 2013 at 05:30:57 UTC, lomereiter wrote:
 On Sunday, 14 July 2013 at 05:04:37 UTC, JS wrote:
 and while I'm at it I need to conditionally constrain types.

 interface A(T) where(!isBasicType!T, (T : B));

 which is suppose to require T to inherit from B if T is not 
 basic type.

 interface A(T) if (isBasicType!T || is(T : B))

 Thanks, works. I remember seeing code like this somewhere but 
 couldn't find any docs about it.

 Here. I admit there should probably be more examples, and 
 perhaps also
 some info on the classes/interfaces/structs & unions pages.

 http://dlang.org/template.html#Constraint

thanks.

"lomereiter" <lomereiter gmail.com> writes:

This should work:

template conditionallyInherit(bool inherit, T) {
     static if (inherit)
         alias T conditionallyInherit;
     else
         interface conditionallyInherit {}
}

"JS" <js.mdnq gmail.com> writes:

On Sunday, 14 July 2013 at 05:28:08 UTC, lomereiter wrote:
 This should work:

 template conditionallyInherit(bool inherit, T) {
     static if (inherit)
         alias T conditionallyInherit;
     else
         interface conditionallyInherit {}
 }

Thanks, I tried something similar but it didn't work right...

I assume that you template ends up creating a dummy interface 
though and this isn't really acceptable.

e.g., interface A : conditionallyInherit!(false, B) { }

will cause A to inherit from conditionallyInherit?

"lomereiter" <lomereiter gmail.com> writes:

 I assume that you template ends up creating a dummy interface 
 though and this isn't really acceptable.

Yes, it does. Once ':' is typed, some inheritance must occur.

Why isn't a dummy interface acceptable?

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

On 07/14/2013 11:37 AM, lomereiter wrote:
 I assume that you template ends up creating a dummy interface though
 and this isn't really acceptable.

 Yes, it does. Once ':' is typed, some inheritance must occur.

Nope.

template Seq(T...){ alias T Seq; }

class C : Seq!(){ }


 Why isn't a dummy interface acceptable?

It creates unnecessary bloat.

template conditionallyInherit(bool inherit, T) {
     static if(inherit) alias T conditionallyInherit;
     else alias Seq!() conditionallyInherit;
}

"lomereiter" <lomereiter gmail.com> writes:

Thanks.
Now I realise that D is much less intuitive than C++.

"Simen Kjaeraas" <simen.kjaras gmail.com> writes:

On 2013-07-14, 07:00, JS wrote:

 I need to conditionally inherit:

 interface A(T) : conditionallyInherit!(isBasicType!T, B);

 A!(double) will inherit B but A!(mytype) won't.

template conditionallyInherit(bool choice, T...) {
     static if (choice) {
         alias conditionallyInherit = T;
     } else {
         import std.typetuple : TypeTuple;
         alias conditionallyInherit = TypeTuple!();
     }
}

Should work.

-- 
Simen