With this code foreach works but foreach_reverse does not:

void main()
{   int[] ints = [2,2,2,5,5,5,4,4,4];
    auto temp = group(ints);
    foreach_reverse(i;temp)
        i[1].writeln;
}

Is this a known issue? Is there a sensible reason for this?

On 05/09/2012 10:50 PM, ixid wrote:
> With this code foreach works but foreach_reverse does not:
>
> void main()
> { int[] ints = [2,2,2,5,5,5,4,4,4];
>   auto temp = group(ints);
>   foreach_reverse(i;temp)
>   i[1].writeln;
> }
>
> Is this a known issue? Is there a sensible reason for this?

group returns a lazy forward range. use foreach(i; group(retro(ints)))

Thanks, sorry to have not understand such a basic point, it's rather hard to get to grips with everything like this in D.

On 05/09/2012 11:33 PM, ixid wrote:
> Thanks, sorry to have not understand such a basic point, it's rather
> hard to get to grips with everything like this in D.
>

No worries.

On Wed, May 09, 2012 at 11:09:15PM +0200, Timon Gehr wrote:
> On 05/09/2012 10:50 PM, ixid wrote:
> >With this code foreach works but foreach_reverse does not:
> >
> >void main()
> >{ int[] ints = [2,2,2,5,5,5,4,4,4];
> >  auto temp = group(ints);
> >  foreach_reverse(i;temp)
> >  i[1].writeln;
> >}
> >
> >Is this a known issue? Is there a sensible reason for this?
> 
> group returns a lazy forward range. use foreach(i; group(retro(ints)))

Yet another reason foreach_reverse needs to go.


T

-- 
It only takes one twig to burn down a forest.

H. S. Teoh:

> Yet another reason foreach_reverse needs to go.

Nope, the specific kind of range of group not being what the OP desired is not foreach_reverse fault.

Bye,
bearophile

>> group returns a lazy forward range. use foreach(i; group(retro(ints)))
> 
> Yet another reason foreach_reverse needs to go.
> 
> 
> T
> 

No please don't! There are hundred and ten very usefull cases.

On Fri, 11 May 2012 03:43:53 -0400, mta`chrono <chrono@mta-international.net> wrote:

>>> group returns a lazy forward range. use foreach(i; group(retro(ints)))
>>
>> Yet another reason foreach_reverse needs to go.
>>
>>
>> T
>>
>
> No please don't! There are hundred and ten very usefull cases.

No, there is only one.

foreach_reverse(i; 0..10) {...}

Every other usage of foreach_reverse can be rewritten with foreach.

I would argue that this should work:

foreach(i; 10..0)

but it would be quite odd given that you would start with 9 and end with 0.  I don't have a really good answer for this, foreach(i; 9..-1) isn't really acceptable, especially if i is unsigned.

-Steve