[phobos] std.datetime and tick types

[Jonathan M Davis]

On Monday 27 September 2010 22:08:12 Robert Jacques wrote:
> On Mon, 27 Sep 2010 11:51:00 -0400, Jonathan M Davis <jmdavisProg at gmx.com>
> Well, if you make up a unit, then you can guarantee no one will have heard
> of it before. And really, learning the hecto SI prefix means someone will
> always understand what hectonanosecond means, as opposed to StdTick or
> Duration, etc, which would have a tendency to be quickly forgotten or
> confused with another library type from another language. As for typing, I
> would expect the 100ns unit to be mainly an internal thing. Most of the
> time I deal in microseconds/1000.0 (i.e. floating point milliseconds),
> when dealing with std.perf today.

Well, it's not entirely made up. 100ns is the tick that Windows uses. So, I 
believe that it's used in C# and other Windows-centric code. So, there is a 
precedent. And while ticks/hectonanoseconds are mostly internal, there are 
certain operations where you're going to want to use them, albeit hopefully 
fairly rarely. The documentation does use the term quite a bit though, 
particularly since std ticks pretty much replace time_t - though that can be a 
bit confusing because time_t is a type which holds the number of milliseconds 
since midnight January 1st, 1970 while std ticks are unit of time which are 100 
ns and are used to hold the time from midnight January 1st, 1 AD.

Maybe, I should replace some of the mentios of ticks with something like StdTime 
(would be an alias for long and hold units of 100 ns with midnight January 1st, 
1 AD as its epoch) and use hectonanosecond where its an issues of units rather 
than type.

Bleh. I don't entirely like any of the options. Having StdTime does seem like a 
good idea, since it does help properly separate the idea of the unit and a type 
with those units from the epoch, but I really don't like hectonanoseconds. It's 
just way too long. milliseconds and microseconds are already seriously pushing 
it. Hectonanoseconds do have the virtue of being explicit however. Some people 
will know what they mean (though I wouldn't expect very many people to), and 
those who don't probably wouldn't have known what ticks indicated anyway, though 
the few people that I've talked to about it haven't liked the idea of having 
hectonanoseconds, since it's really ugly.

- Jonathan M Davis