void foo(out char[32] test)
{
}

DMD gives the error that char[32] can't be an out parameter.

I realize arrays are passed by reference implicitly.  I was after more of the behavior you get when you return an array, but without the temporary.

char[32] foo()
{
    char[32] result;
    return result;
}

Oh well.  I think it's by design.

Sean

Hmm. Then, how does one modify an array in D
without copying (besides wrapping it in a class)?

Luna Kid

"Sean L. Palmer" <palmer.sean@verizon.net> wrote in message news:b6h0ql$2tva$1@digitaldaemon.com...
> void foo(out char[32] test)
> {
> }
>
> DMD gives the error that char[32] can't be an out parameter.
>
> I realize arrays are passed by reference implicitly.  I was after more of the behavior you get when you return an array, but without the temporary.
>
> char[32] foo()
> {
>     char[32] result;
>     return result;
> }
>
> Oh well.  I think it's by design.
>
> Sean
>
>

"Luna Kid" <lunakid@neuropolis.org> wrote in message news:b6h9nv$21k$1@digitaldaemon.com...
> Hmm. Then, how does one modify an array in D
> without copying (besides wrapping it in a class)?

arrays are not arrays in the java/C sense, they are slices

int[] foo = new int[40];
equiv to
struct array { T * start; int length; }
foo.start = (int*)calloc( 40, sizeof(int) );
foo.length = 40;

int func( int[] parm ) ...

is equiv to the C
int func( struct array param ) ...

so you get the start and length, which allows modifications to data but not length (just like delphi open arrays).

arrays can be inout they can not be out I assume because that would cause implict allocations

you can get out without copying with
char[] func() {
    char[] foo = new char[32];
    return foo[0..32];
}

a work of warning do not be tempted to write

char[] func( ){
    char [32] foo;
    return foo[0..32];
}
will return a slice alllowing access to the stack :)




>
> Luna Kid
>
> "Sean L. Palmer" <palmer.sean@verizon.net> wrote in message news:b6h0ql$2tva$1@digitaldaemon.com...
> > void foo(out char[32] test)
> > {
> > }
> >
> > DMD gives the error that char[32] can't be an out parameter.
> >
> > I realize arrays are passed by reference implicitly.  I was after more
of
> > the behavior you get when you return an array, but without the
temporary.
> >
> > char[32] foo()
> > {
> >     char[32] result;
> >     return result;
> > }
> >
> > Oh well.  I think it's by design.
> >
> > Sean
> >
> >
>
>

> arrays can be inout ...

Ahh, I missed that one, sorry...

Thanks!
Luna Kid

Sean L. Palmer wrote:
> void foo(out char[32] test)
> {
> }
> 
> DMD gives the error that char[32] can't be an out parameter.

Static arrays can't be out parameters; making it a dynamic array will work fine.  I think it's a compiler limitation, not lingual.

> I realize arrays are passed by reference implicitly.  I was after more of
> the behavior you get when you return an array, but without the temporary.

Static arrays are passed by content.  I think the optimiser already does temporary return value removal.  Walter said something along these lines in that thread advocating return variables, and it looks like a fairly easy one to pull off.

Burton Radons wrote:
> 
> Sean L. Palmer wrote:
> > void foo(out char[32] test)
> > {
> > }
> >
> > DMD gives the error that char[32] can't be an out parameter.
> 
> Static arrays can't be out parameters; making it a dynamic array will work fine.  I think it's a compiler limitation, not lingual.
                             ---------------------------------

Sorry, could you explain this. Do you think the D specification would
allow it but it is not implemented?

> > I realize arrays are passed by reference implicitly.  I was after more of the behavior you get when you return an array, but without the temporary.
> 
> Static arrays are passed by content.

In any case? Or does this depend on in/out/inout?

Only for small arrays this might make sense. I about 95% of all cases the C way of passing arrays by reference is more appropriate with respect to performance.

> I think the optimiser already does
> temporary return value removal.  Walter said something along these lines
> in that thread advocating return variables, and it looks like a fairly
> easy one to pull off.

Could you give me a hint how to find this thread?

-- 
Helmut Leitner    leitner@hls.via.at
Graz, Austria   www.hls-software.com