http://d.puremagic.com/issues/show_bug.cgi?id=6725

           Summary: core.time.dur should accept floating point
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: druntime
        AssignedTo: nobody@puremagic.com
        ReportedBy: siegelords_abode@yahoo.com


--- Comment #0 from siegelords_abode@yahoo.com 2011-09-24 14:15:18 PDT ---
I'd prefer to be able to do this:

dur!("secs")(1.0);
dur!("secs")(1.5);
dur!("secs")(1.5001);

instead of having to do this:

dur!("secs")(1);
dur!("msecs")(1500);
dur!("nsecs")(1500100);

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich@gmail.com,
                   |                            |jmdavisProg@gmx.com


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-08 17:48:37 PST ---
CC-ing jmdavis: Is it worth of adding this? This is your area of expertise. :)

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--- Comment #2 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-08 17:49:08 PST ---
(In reply to comment #1)
> worth of adding

*worth adding

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--- Comment #3 from Jonathan M Davis <jmdavisProg@gmx.com> 2013-02-08 18:23:30 PST ---
In general, using floating point values like that is asking for trouble, because you're going to run into precision problems. It's far better to use integral values with the more precise units, but I can see why someone would want to be able to do this. It wouldn't be all that big a deal to add it, and it's probably worth having. It's just of questionable value if you actually want to be precise.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla@digitalmars.com


--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> 2013-02-08 21:53:30 PST ---
Mixing in floating point into what are properly integer operations is nothing but trouble.

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--- Comment #5 from Jonathan M Davis <jmdavisProg@gmx.com> 2013-02-08 22:26:54 PST ---
Without dur or convert taking floating point values, you're forced to do something like

auto d = dur!"hnsecs"(cast(long)(convert!("seconds", "hnsecs")(1) * 1.5001)));

which is arguably overly verbose, but I really don't think that using floating point values for time should be encouraged at all. So, it could definitely be more user friendly, but I'm not sure that doing so would be a good idea. Too many people already seem willing to use floating point values for time (they did in the code base that I work on at work until I ported SysTime and Duration to C++ for work). So, I don't know what the right balance of user friendliness and good practice is in this case.

TickDuration _does_ support some floating point stuff, but only converting _to_ them, not from them, and it's essentially a fraction internally. Though if I could go back, I probably would have gotten rid of TickDuration rather than integrating it into std.datetime, since I really don't think that it buys us much over Duration (hnsecs is already better precision than most system clocks anyway), and the fact that it's basically a fraction has caused quite a bit of trouble. It's particularly nasty when it comes to trying to test it.

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--- Comment #6 from Walter Bright <bugzilla@digitalmars.com> 2013-02-08 23:04:15 PST ---
1. Using floating point for time is like using floating point for accounting software ($57.23). It doesn't work for things that come in discrete quanta (pennies, clock ticks). You will spend FAR more time chasing weird problems than you will save in "convenience". Yes, I have experience with this, and I understand floating point (having build FP emulators).

2. Many machines have very poor FP performance compared with integer performance. Implementing basic operations using unnecessary FP results in slow, bloated code.

3. Phobos' time functions are already massively complex. I still can't even compile the datetime unittests on a 512Mb machine. Please, no more.

4. It's trivial for a user to write their own FP wrapper around dur. There is no reason to integrate this into dur itself. Software should be pieced together using layers of abstraction, not kitchen sink base types.

5. It would take longer to read the documentation for this enhancement than to just convert your floating point value to an int.

6. You're not forced to write long complicated expressions to convert fp to integers. It's just a scale and a cast:

    dur!("secs")(1.5001) => dur!("nsecs")(cast(long)(1.5001 * 1000000));

I.e. I feel pretty strongly this is a bad idea for Phobos.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


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