protocol for using InputRanges

[Walter Bright]

On 3/27/2014 12:21 PM, Rainer Schuetze wrote:
> This loop is intuitive. Not being allowed to call empty or front multiple times
> or not at all is unintuitive. They should not be named as if they are properties
> then.

I can concede that. But I can't concede being able to call front without first 
calling empty, or calling popFront without calling empty and front, or requiring 
'pump priming' in the constructor.