protocol for using InputRanges

[Walter Bright]

On 3/27/2014 9:12 AM, monarch_dodra wrote:
> If you initialized the next element in both constructor

As mentioned earlier, requiring this of a range constructor makes it impossible 
to separate composition of a range with using it.

As also mentioned earlier, this throws under the bus entire categories of use 
cases for ranges, all to avoid a single call to 'empty'.