Is there a reason the language spec disallows this?

----
void main(){
auto a=mixin("1");//OK
alias b=a;//OK
mixin("alias c=a;");//OK
// alias c=mixin("a");//NG : Error: basic type expected, not mixin
}
----

On 06/22/2013 09:52 PM, Timothee Cour wrote:
> Is there a reason the language spec disallows this?
>
> ----
> void main(){
>     auto a=mixin("1");//OK
>     alias b=a;//OK
>     mixin("alias c=a;");//OK
>     // alias c=mixin("a");//NG : Error: basic type expected, not mixin
> }
> ----

No, it is arbitrary.

On Sat, Jun 22, 2013 at 2:47 PM, Timon Gehr <timon.gehr@gmx.ch> wrote:

> On 06/22/2013 09:52 PM, Timothee Cour wrote:
>
>> Is there a reason the language spec disallows this?
>>
>> ----
>> void main(){
>>     auto a=mixin("1");//OK
>>     alias b=a;//OK
>>     mixin("alias c=a;");//OK
>>     // alias c=mixin("a");//NG : Error: basic type expected, not mixin
>> }
>> ----
>>
>
> No, it is arbitrary.
>

that's what i thought!
same with template mixin's being restricated.

... can we fix it?

it makes for cleaner code.

On 06/22/2013 11:51 PM, Timothee Cour wrote:
>
>
> On Sat, Jun 22, 2013 at 2:47 PM, Timon Gehr <timon.gehr@gmx.ch
> <mailto:timon.gehr@gmx.ch>> wrote:
>
>     On 06/22/2013 09:52 PM, Timothee Cour wrote:
>
>         Is there a reason the language spec disallows this?
>
>         ----
>         void main(){
>              auto a=mixin("1");//OK
>              alias b=a;//OK
>              mixin("alias c=a;");//OK
>              // alias c=mixin("a");//NG : Error: basic type expected,
>         not mixin
>         }
>         ----
>
>
>     No, it is arbitrary.
>
>
> that's what i thought!
> same with template mixin's being restricated.
>

?

> ... can we fix it?
>
> it makes for cleaner code.
>

It surely could be fixed if you want to spend the time hacking on DMD.
I think the grammar is somewhat poorly designed in general.

On Sat, Jun 22, 2013 at 2:55 PM, Timon Gehr <timon.gehr@gmx.ch> wrote:

> On 06/22/2013 11:51 PM, Timothee Cour wrote:
>
>>
>>
>> On Sat, Jun 22, 2013 at 2:47 PM, Timon Gehr <timon.gehr@gmx.ch <mailto:timon.gehr@gmx.ch>> wrote:
>>
>>     On 06/22/2013 09:52 PM, Timothee Cour wrote:
>>
>>         Is there a reason the language spec disallows this?
>>
>>         ----
>>         void main(){
>>              auto a=mixin("1");//OK
>>              alias b=a;//OK
>>              mixin("alias c=a;");//OK
>>              // alias c=mixin("a");//NG : Error: basic type expected,
>>         not mixin
>>         }
>>         ----
>>
>>
>>     No, it is arbitrary.
>>
>>
>> that's what i thought!
>> same with template mixin's being restricated.
>>
>>
> ?
>
>
they're restricted to declarations. I don't see the need for such restriction.



>  ... can we fix it?
>>
>> it makes for cleaner code.
>>
>>
> It surely could be fixed if you want to spend the time hacking on DMD. I think the grammar is somewhat poorly designed in general.
>

On 2013-06-22 23:47, Timon Gehr wrote:

> No, it is arbitrary.

I think the spec says you can only mixin whole expression. But for some reason you can use a mixin in a __traits expression without having the whole expression in a mixin.

-- 
/Jacob Carlborg

On 06/23/2013 11:32 AM, Jacob Carlborg wrote:
> On 2013-06-22 23:47, Timon Gehr wrote:
>
>> No, it is arbitrary.
>
> I think the spec says you can only mixin whole expression.

That only means you cannot do things like eg:

mixin("a*"); mixin("b");

but instead you need to do:

mixin("a*b");

such that the string content forms a valid expression according to the grammar.


> But for some
> reason you can use a mixin in a __traits expression without having the
> whole expression in a mixin.
>

Example?

On 2013-06-23 13:27, Timon Gehr wrote:

> Example?

@(3) int a;
alias Tuple!(__traits(getAttributes, mixin("a"))) attrs;

-- 
/Jacob Carlborg