how to round durations to most significant unit ? (5 secs, 889 ms, and 811 μs => 5 secs)

[Jonathan M Davis]

On Saturday, February 15, 2014 22:13:07 Steven Schveighoffer wrote:
> On Fri, 14 Feb 2014 17:14:03 -0500, Jonathan M Davis <jmdavisProg at gmx.com>
> 
> wrote:
> > On Thursday, February 13, 2014 23:37:13 Timothee Cour wrote:
> >> Is there a function to do this?
> >> If not and I/someone writes it, is there interest to add it to
> >> std.datetime?
> >> 
> >> Duration t = ...;
> >> t.to!string => 5 secs, 889 ms, and 811 μs
> >> t.round.to!string    => 5 secs
> >> 
> >> t=...;
> >> t.to!string => 889 ms, and 811 μs
> >> t.round.to!string    => 889 secs
> >> 
> >> Use case: shorter logs.
> > 
> > There is no function for that, and no one's ever asked for anything like
> > it,
> > so I don't know how worthwhile it is to add. However, one possible
> > implementation would be
> > 
> > auto roundToLargest(Duration d)
> > {
> > 
> >     foreach(units; TypeTuple!("weeks", "days", "hours", "minutes",
> >                               "seconds", "msecs", "usecs"))
> >     
> >     {
> >     
> >         immutable value = d.total!units();
> >         if(value != 0)
> >         
> >             return dur!units(value);
> >     
> >     }
> >     
> >     return d;
> > 
> > }
> 
> You are doing the calculation for every test.
> 
> Better:
> if(d >= dur!units(1))
>     ...

Yeah. That would be better.

> Now, I think that the dur!units(1) should be statically determined, but if
> not, I think you could make it statically determined via enum.

It'll only be statically determined if it's in a context that requires it. 
Unless something has changed recently, the compiler never tries to do CTFE if 
it doesn't have to. So, you'd need to use an enum to force it.

- Jonathan M Davis