protocol for using InputRanges

[RivenTheMage]

On Thursday, 27 March 2014 at 21:54:00 UTC, Andrei Alexandrescu
wrote:
> On 3/27/14, 1:58 PM, Walter Bright wrote:
>> On 3/27/2014 12:50 PM, Andrei Alexandrescu wrote:
>>> Yah, agreed. -- Andrei
>>
>> Completely unworkable. To determine if a range is empty or 
>> not, it may
>> have to actually read from its input. TTYs are an example. 
>> Although
>> empty may then cache the result, and not read the second time 
>> it is
>> called, an observer of TTY could see that an item was read 
>> from the TTY.
>
> That's a good point too.
>
> Andrei

Maybe new kind of range can help?
Which has "bool popFront()" instead of "bool empty() + void
popFront()".