[phobos] Problem with definition of isInfinite(Range)

[Jonathan M Davis]

Okay. If I understand correctly, as it stands, a range type is either infinite or 
its not, and it's known at compile-time whether it's infinite or not. This 
appears to be done by checking for a static property empty of type bool which is 
known at compile-time. The question is do we _need_ to know at compile-time 
whether a range is infinite? Or it would it be possible to make it so that that 
can be determined at runtime?

My guess is that the algorithms that care need to know at compile-time, but if 
that's the case, it poses a definite problem for me.

I have been working on a date/time module for potential inclusion in Phobos. 
Part of that includes a time interval which represents a period of time starting 
at one point of time and extending to another point of time which is not 
included in the interval. So, for example [2010-07-04 - 2010-08-03). I'm working 
on creating ranges to iterate over a time interval. The problem is that an 
interval can be infinite, but you don't know at compile time whether it's 
infinite. You could have an interval such as [2010-07-04 - positive infinity), and 
a range over that interval would be infinite. However, whether a given interval 
(and thus its range) is infinite depends on the runtime arguments that created 
the interval. So, I have no way of creating an infinite range for which 
isInfinite(Range) will return true.

Would it be reasonable to make it possible to have infinite ranges which were 
determined to be infinite at runtime rather than compile-time? Or is there a 
better solution? Or is it simply tough luck, and the range may be effectively 
infinite but can't be treated that way by algorithms using isInfinite(Range)?

- Jonathan M Davis