I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
Oddly enough, you cannot define a template in the same way

I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.

Walter, is this the correct behaviour?

The following compiles ok
##
void main()
{
    enum X
    {
        A,
        B,
    }

    struct Y
    {
        int x;
        int y;
        char a;
    }

    class R
    {
        Y g;
        X d;
    }

}
##/

but the following doesn't work
##
void main()
{
    class R
    {
        Y g;
        X d;
    }

    template kill(X)
    {
        void kill()
        {
        }
    }
}
##/

gives the following error messeges:
#  found 'template' instead of statement

Hasan Aljudy wrote:
> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
> Oddly enough, you cannot define a template in the same way
> 
> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
> 
> Walter, is this the correct behaviour?

It is.  Templates are merely a special case as they must have external linkage.


Sean

Hey guys,

My parser (based on 0.149) allows the first example and rejects the second. Thus the grammar that I have seems to confirm what Sean has said, as well.

If anyone wants a copy of the pre-release (based on the Elkhound GLR parser generator) then just email me at:

wilsonk-at-cpsc-dot-ucalgary-dot-ca

Thanks,
Kelly Wilson

P.S. Ivan (or BCS), if you want an update then please email (I have fixed about
7 or 8 problems from the original...though there are still some minor things to
clean up).

In article <e321m5$100h$1@digitaldaemon.com>, Sean Kelly says...
>
>Hasan Aljudy wrote:
>> I don't know if this is a bug or what, but for some reason, dmd allows
>> you to define classes/structs/unions/enums as statements inside function
>> bodies.
>> Oddly enough, you cannot define a template in the same way
>> 
>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>> 
>> Walter, is this the correct behaviour?
>
>It is.  Templates are merely a special case as they must have external linkage.
>
>
>Sean

kellywilson@nowhere.com wrote:
> Hey guys,
> 
> My parser (based on 0.149) allows the first example and rejects the second. Thus
> the grammar that I have seems to confirm what Sean has said, as well.
> 
> If anyone wants a copy of the pre-release (based on the Elkhound GLR parser
> generator) then just email me at:
> 
> wilsonk-at-cpsc-dot-ucalgary-dot-ca

I'm sort of working on my own parser ;)
btw I study at UofC too!!

> 
> Thanks,
> Kelly Wilson
> 
> P.S. Ivan (or BCS), if you want an update then please email (I have fixed about
> 7 or 8 problems from the original...though there are still some minor things to
> clean up).
> 
> In article <e321m5$100h$1@digitaldaemon.com>, Sean Kelly says...
> 
>>Hasan Aljudy wrote:
>>
>>>I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>>>Oddly enough, you cannot define a template in the same way
>>>
>>>I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>>
>>>Walter, is this the correct behaviour?
>>
>>It is.  Templates are merely a special case as they must have external linkage.
>>
>>
>>Sean
> 
> 
> 

Sean Kelly wrote:
> Hasan Aljudy wrote:
>> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>> Oddly enough, you cannot define a template in the same way
>>
>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>
>> Walter, is this the correct behaviour?
> 
> It is.  Templates are merely a special case as they must have external linkage.
> 
> 
> Sean

What do you mean by that? What is external linkage? Did you meant an extern(al) storage class? (I just found out now something I unknew, that are two distinct "extern" keywords/concepts in D)
And how exactly does that restricts templates not being allowed inside functions?

-- 
Bruno Medeiros - CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

Bruno Medeiros wrote:
> Sean Kelly wrote:
>> Hasan Aljudy wrote:
>>> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>>> Oddly enough, you cannot define a template in the same way
>>>
>>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>>
>>> Walter, is this the correct behaviour?
>>
>> It is.  Templates are merely a special case as they must have external linkage.
> 
> What do you mean by that? What is external linkage? Did you meant an extern(al) storage class? (I just found out now something I unknew, that are two distinct "extern" keywords/concepts in D)
> And how exactly does that restricts templates not being allowed inside functions?

External linkage means that a symbol is visible from another module. But I mis-spoke.  Template parameters must have external linkage. Templates themselves may only be defined at module or class scope.  This is a carryover from C++, and I'm not certain whether there's a technical obstacle to function-scope templates or not.  There doesn't seem to be, but then I've never implemented template support in a compiler before. Perhaps Walter could explain further.


Sean

Sean Kelly wrote:
> Bruno Medeiros wrote:
>> Sean Kelly wrote:
>>> Hasan Aljudy wrote:
>>>> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>>>> Oddly enough, you cannot define a template in the same way
>>>>
>>>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>>>
>>>> Walter, is this the correct behaviour?
>>>
>>> It is.  Templates are merely a special case as they must have external linkage.
>>
>> What do you mean by that? What is external linkage? Did you meant an extern(al) storage class? (I just found out now something I unknew, that are two distinct "extern" keywords/concepts in D)
>> And how exactly does that restricts templates not being allowed inside functions?
> 
> External linkage means that a symbol is visible from another module. But I mis-spoke.  Template parameters must have external linkage. Templates themselves may only be defined at module or class scope.  This is a carryover from C++, and I'm not certain whether there's a technical obstacle to function-scope templates or not.  There doesn't seem to be, but then I've never implemented template support in a compiler before. Perhaps Walter could explain further.

There's some weird stuff in there. Mixins can be local, and because of alias template parameters, there's a name mangling for templates which are defined local to functions.

Don Clugston wrote:
> Sean Kelly wrote:
>> Bruno Medeiros wrote:
>>> Sean Kelly wrote:
>>>> Hasan Aljudy wrote:
>>>>> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>>>>> Oddly enough, you cannot define a template in the same way
>>>>>
>>>>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>>>>
>>>>> Walter, is this the correct behaviour?
>>>>
>>>> It is.  Templates are merely a special case as they must have external linkage.
>>>
>>> What do you mean by that? What is external linkage? Did you meant an extern(al) storage class? (I just found out now something I unknew, that are two distinct "extern" keywords/concepts in D)
>>> And how exactly does that restricts templates not being allowed inside functions?
>>
>> External linkage means that a symbol is visible from another module. But I mis-spoke.  Template parameters must have external linkage. Templates themselves may only be defined at module or class scope.  This is a carryover from C++, and I'm not certain whether there's a technical obstacle to function-scope templates or not.  There doesn't seem to be, but then I've never implemented template support in a compiler before. Perhaps Walter could explain further.
> 
> There's some weird stuff in there. Mixins can be local, and because of alias template parameters, there's a name mangling for templates which are defined local to functions.

There are no templates *defined* local to functions. Did you mean mixin instantiations?
I think (normal) template instances are quite different from mixin instances in that regard. Mixin instances have copy-paste behaviour and are each unique, and the mixin name part has no name-magling at all in the case of an anonymous mixin, or has the name which is defined in the named mixin. (Normal) template instances have name-mangling dependent on  the template arguments, because that is what _identifies_ the template instance. There is no such parallel with mixins, as they are unique.
I can't test any of these suppositions yet, as I can't check the .obj's symbols or ASM (I'm planning to get the EUP soon), but I'm fairly sure it's something more or less like this.

-- 
Bruno Medeiros - CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

Sean Kelly wrote:
> Bruno Medeiros wrote:
>> Sean Kelly wrote:
>>> Hasan Aljudy wrote:
>>>> I don't know if this is a bug or what, but for some reason, dmd allows you to define classes/structs/unions/enums as statements inside function bodies.
>>>> Oddly enough, you cannot define a template in the same way
>>>>
>>>> I didn't find in the docs any mention of whether aggregates are allowed inside function bodies or not.
>>>>
>>>> Walter, is this the correct behaviour?
>>>
>>> It is.  Templates are merely a special case as they must have external linkage.
>>
>> What do you mean by that? What is external linkage? Did you meant an extern(al) storage class? (I just found out now something I unknew, that are two distinct "extern" keywords/concepts in D)
>> And how exactly does that restricts templates not being allowed inside functions?
> 
> External linkage means that a symbol is visible from another module. But I mis-spoke.  Template parameters must have external linkage. Templates themselves may only be defined at module or class scope.  This is a carryover from C++, and I'm not certain whether there's a technical obstacle to function-scope templates or not.  There doesn't seem to be, but then I've never implemented template support in a compiler before. Perhaps Walter could explain further.
> 
> 
> Sean

I see. Hum, can a local variable (local to a function) be external?

-- 
Bruno Medeiros - CS/E student
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

Bruno Medeiros wrote:
> 
> I see. Hum, can a local variable (local to a function) be external?

Sort of.  A static local variable has external linkage in D (and I think in C++ as well, though the meaning of 'static' is a bit different there).  Here's an example:

    import std.c.stdio;

    template templ( alias A )
    {
        void templ()
        {
            printf( "%i\n", A );
        }
    }

    int i = 5;

    void main()
    {
        templ!(i);

        int j = 6;
        templ!(j);
    }

Change the "int j = 6" to "static int j = 6" and everything compiles.


Sean