Re: Conditional Inheritance

2013-07-15 Thread lomereiter 

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

Re: Conditional Inheritance

2013-07-14 Thread lomereiter 
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?

Re: Conditional Inheritance

2013-07-14 Thread Simen Kjaeraas 

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

Re: Conditional Inheritance

2013-07-14 Thread Simen Kjaeraas 

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

Re: Conditional Inheritance

2013-07-14 Thread Timon Gehr 

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;
}

Conditional Inheritance

2013-07-13 Thread JS 

I need to conditionally inherit:

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

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

Re: Conditional Inheritance

2013-07-13 Thread JS 

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.

Re: Conditional Inheritance

2013-07-13 Thread lomereiter 

This should work:

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

Re: Conditional Inheritance

2013-07-13 Thread lomereiter 

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))

Re: Conditional Inheritance

2013-07-13 Thread JS 

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?

Re: Conditional Inheritance

2013-07-13 Thread JS 

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.