Function std.datetime.interval.Interval.fwdRange
Returns a range which iterates forward over the interval, starting
at begin, using func to generate each successive time
point.
IntervalRange!(TP,Direction.fwd) fwdRange
(
TP delegate(in TP) func,
PopFirst popFirst = PopFirst
) const;
The range's front is the interval's begin. func is
used to generate the next front when popFront is called. If
popFirst is PopFirst, then popFront is called
before the range is returned (so that front is a time point which
func would generate).
If func ever generates a time point less than or equal to the
current front of the range, then a
DateTimeException will be thrown. The range
will be empty and iteration complete when func generates a
time point equal to or beyond the end of the interval.
There are helper functions in this module which generate common
delegates to pass to fwdRange. Their documentation starts with
"Range-generating function," making them easily searchable.
Parameters
| Name | Description |
|---|---|
| func | The function used to generate the time points of the range over the interval. |
| popFirst | Whether popFront should be called on the range
before returning it. |
Throws
DateTimeException if this interval is
empty.
Warning
func must be logically pure. Ideally, func
would be a function pointer to a pure function, but forcing
func to be pure is far too restrictive to be useful, and
in order to have the ease of use of having functions which generate
functions to pass to fwdRange, func must be a
delegate.
If func retains state which changes as it is called, then
some algorithms will not work correctly, because the range's
save will have failed to have really saved the range's state.
To avoid such bugs, don't pass a delegate which is
not logically pure to fwdRange. If func is given the
same time point with two different calls, it must return the same
result both times.
Of course, none of the functions in this module have this problem, so it's only relevant if when creating a custom delegate.
Example
auto interval = Interval!Date(Date(2010, 9, 1), Date(2010, 9, 9));
auto func = delegate (in Date date) // For iterating over even-numbered days.
{
if ((date