On Tuesday, 1 April 2014 at 10:54:41 UTC, Jonathan M Davis wrote:
On Tuesday, April 01, 2014 05:35:28 ed wrote:
OK, lazy me just read the std.satetime article again. It
appears
the design is for no invalid values and it is currently a known
limitation due to CTFE.
---
d_time_nan There is no equivalent. SysTime.init, which has a
null
TimeZone object, would be the closest, but once CTFE advances
to
the point that you can new up class objects with it,
SysTime.init's timezone will be LocalTime, so don't rely on
SysTime.init being invalid. std.datetime in general tries to
avoid having any invalid states for any of its types. It's
intended that creating such values be impossible.
---
I would still like to know if there is a way around this so I
can
have my struct default init.
You can certainly have a struct with a SysTime member, but
there's no way for
it to use that SysTime without first assigning a valid value to
it - at least,
not without segfaulting when it tries to use the SysTime in any
context which
it would use its timezone member.
If you really want to have the SysTime be useable in the init
value of your
struct, then you can make it so that each of its member
functions which use
the SysTime member check it for validity first (or have a
separate bool which
indicates whether the SysTime has been assigned to or not), in
which case, it
could assign something like SysTime(0) to it, which would be
the valid
equivalent of SysTime.init.
Unfortunately, that does add extra overhead, but there isn't
any way around it
if you want to have the SysTime be used without having the user
of the struct
assign to it first. It's pretty much the same boat that SysTime
itself is in.
I could make it so that it checks the timezone for null every
time it's used
and assign LocalTime to it if it's null, but that adds constant
overhead. My
decision was that it was better to just live with the fact that
SysTime.init
is invalid. It's debatable though, as it's a trade-off.
- Jonathan M Davis
I have changed my code slightly to what you suggest, assigning
SysTime(0) if not initialised. It wasn't a big change and works
fine.
Thanks,
ed
