Is this range behaviour correct?

[Andrea Fontana]

On Thursday, 14 March 2013 at 13:58:56 UTC, monarch_dodra wrote:
> On Thursday, 14 March 2013 at 13:20:51 UTC, Andrea Fontana 
> wrote:
>> On Thursday, 14 March 2013 at 12:29:26 UTC, Andrei 
>> Alexandrescu wrote:
>>> On 3/14/13 6:45 AM, Andrea Fontana wrote:
>>>> On Thursday, 14 March 2013 at 10:08:53 UTC, Andrea Fontana 
>>>> wrote:
>>>>> I'm trying to implement a db cursor as simple InputRange. I 
>>>>> can't
>>>>> implement as forward range because using c-api I can't 
>>>>> clone/save cursor.
>>> Add .save() to it.
>>>
>>> Andrei
>>
>> I can't add save and create a forward range: c-api doesn't 
>> allow me to clone db cursor.
>
> But think about it. You say you can't save, but you want pass 
> by value to preserve state. If you can preserve state, doesn't 
> that mean you just saved?
>
> Once you've passed your "can't preserve state" to a foreach, 
> then your range is consumed. So yes, it is correct behavior.
>
> Most input ranges should model reference semantics when 
> passed/copied by value. If somebody modifies the range, all 
> ranges are affected. The tough part is usually preserving 
> correct state.

I was hoping there's something I didn't know like rewind() to 
implement :)

Ok, I'll pray db developer to add a clone method or I'll use 
something like

auto res = cursor.array(); if needed