A range over a PosInfInterval. It is an infinite range.

PosInfIntervalRange is only ever constructed by PosInfInterval. However, when it is constructed, it is given a function, func, which is used to generate the time points which are iterated over. func takes a time point and returns a time point of the same type. For instance, to iterate over all of the days in the interval PosInfInterval!Date, pass a function to PosInfInterval's fwdRange where that function took a std.datetime.date.Date and returned a std.datetime.date.Date which was one day later. That function would then be used by PosInfIntervalRange's popFront to iterate over the std.datetime.date.Dates in the interval - though obviously, since the range is infinite, use a function such as std.range.take with it rather than iterating over all of the dates.

As the interval goes to positive infinity, the range is always iterated over forwards, never backwards. func must generate a time point going in the proper direction of iteration, or a std.datetime.date.DateTimeException will be thrown. So, the time points that func generates must be later in time than the one passed to it. If it's either identical or earlier in time, then a std.datetime.date.DateTimeException will be thrown.