joiner and map, strange behavior

[Stephan Schiffels]

Am 12.03.13 20:22, schrieb Timon Gehr:
> On 03/12/2013 06:51 PM, Stephan Schiffels wrote:
>> ...
>>
>> Thanks, I had a brief look at std.algorithm.joiner but couldn't find
>> anything obvious, maybe I should look deeper into it.
>> ...
>
> I guess it is because of the following:
>
> Eg (similar code occurs two times):
> ...
>      if (_sep.empty)
>      {
>          // Advance to the next range in the
>          // input
>          //_items.popFront();
>          for (;; _items.popFront())
>          {
>              if (_items.empty) return;
>              if (!_items.front.empty) break; // front called
>          }
>          _current = _items.front; // front called again
>          _items.popFront();
>      }
> ...
>
> The code should only call front once for the first non-empty range.
>
> Presumed example fix (though the implementation seems rather clumsy and
> should probably be replaced completely):
>
> ...
>      if (_sep.empty)
>      {
>          // Advance to the next range in the
>          // input
>          //_items.popFront();
>          for (;; _items.popFront())
>          {
>              if (_items.empty) return;
>              _current = _items.front;
>              if (!_current.empty) break;
>          }
>          _items.popFront();
>      }
> ...

Thanks, that's very clear now. I stumbled over it because the function I 
call loads a lot of data and a factor 2 makes all the difference in 
runtime. Maybe I should file a bug report or at least a request to 
improve this.

Stephan