Following simple program fails to compile with latest DMD 2.041 (In fact it fails to compile with any dmd2 version i have tried):

"test.d"
> import std.stdio;
> import std.range;
> import std.algorithm;
>
> int main()
> {
>   auto test = stride( iota(0,10,1) , 2 );
>   return 0;
> }

Output:
[mist@mistwork d]$ dmd -run test.d
/usr/include/d/std/range.d(716): Error: this._input.front() is not an lvalue
/usr/include/d/std/range.d(724): Error: this._input.back() is not an lvalue


Is it a bug? I managed to get stride working only on arrays. If it is the supposed way to work, how can be similar filtering done on ranges?

Mihail Strashun wrote:
> Following simple program fails to compile with latest DMD 2.041 (In fact it fails to compile with any dmd2 version i have tried):
> 
> "test.d"
>  > import std.stdio;
>  > import std.range;
>  > import std.algorithm;
>  >
>  > int main()
>  > {
>  >   auto test = stride( iota(0,10,1) , 2 );
>  >   return 0;
>  > }
> 
> Output:
> [mist@mistwork d]$ dmd -run test.d
> /usr/include/d/std/range.d(716): Error: this._input.front() is not an lvalue
> /usr/include/d/std/range.d(724): Error: this._input.back() is not an lvalue
> 
> 
> Is it a bug? I managed to get stride working only on arrays. If it is the supposed way to work, how can be similar filtering done on ranges?


It's definitely a bug.  I've reported it:

http://d.puremagic.com/issues/show_bug.cgi?id=3894

-Lars

Thanks!

Lars T. Kyllingstad wrote:
> Mihail Strashun wrote:
>> Following simple program fails to compile with latest DMD 2.041 (In fact it fails to compile with any dmd2 version i have tried):
>>
>> "test.d"
>>  > import std.stdio;
>>  > import std.range;
>>  > import std.algorithm;
>>  >
>>  > int main()
>>  > {
>>  >   auto test = stride( iota(0,10,1) , 2 );
>>  >   return 0;
>>  > }
>>
>> Output:
>> [mist@mistwork d]$ dmd -run test.d
>> /usr/include/d/std/range.d(716): Error: this._input.front() is not an lvalue
>> /usr/include/d/std/range.d(724): Error: this._input.back() is not an lvalue
>>
>>
>> Is it a bug? I managed to get stride working only on arrays. If it is the supposed way to work, how can be similar filtering done on ranges?
> 
> 
> It's definitely a bug.  I've reported it:
> 
> http://d.puremagic.com/issues/show_bug.cgi?id=3894
> 
> -Lars

On Mon, Mar 8, 2010 at 13:00, Lars T. Kyllingstad <public@kyllingen.nospamnet> wrote:

> It's definitely a bug.  I've reported it:
>
> http://d.puremagic.com/issues/show_bug.cgi?id=3894


std.range use ref everywhere. I had to comment them out to get any composition to work. But the 'auto ref' feature added a release ago was made to solve this problem, I guess. Full-blown propagation of ref when you can have it, graceful stop when you cannot.

Hmm, I should try this as soon as I won't have a baby sleeping on me...

Philippe Sigaud wrote:
> 
> 
> On Mon, Mar 8, 2010 at 13:00, Lars T. Kyllingstad <public@kyllingen.nospamnet> wrote:
> 
>     It's definitely a bug.  I've reported it:
> 
>     http://d.puremagic.com/issues/show_bug.cgi?id=3894
> 
> 
> std.range use ref everywhere. I had to comment them out to get any composition to work. But the 'auto ref' feature added a release ago was made to solve this problem, I guess. Full-blown propagation of ref when you can have it, graceful stop when you cannot.
> 
> Hmm, I should try this as soon as I won't have a baby sleeping on me...
> 

Hm, changing "ref" on lines 716 and 724 to "auto ref" changes nothing. Changing it to simply "auto" seems to solve problem.

How "auto ref" feature is supposed to work? This ( http://www.digitalmars.com/d/2.0/function.html ) description tends to match problem with stride, but as I have just said, it gives same error.

On Fri, Mar 26, 2010 at 11:16, Mihail Strashun <m.strashun@gmail.com> wrote:

> Hm, changing "ref" on lines 716 and 724 to "auto ref" changes nothing. Changing it to simply "auto" seems to solve problem.
>
> How "auto ref" feature is supposed to work? This ( http://www.digitalmars.com/d/2.0/function.html ) description tends to match problem with stride, but as I have just said, it gives same error.
>

Then we both do not understand what auto ref functions can do. Or maybe it's still a bit buggy?