Re: core.time Duration how to get units in double/float format?
On Tuesday, January 19, 2016 14:07:50 Borislav Kosharov via Digitalmars-d-learn
wrote:
> On Monday, 18 January 2016 at 12:46:31 UTC, Jonathan M Davis
> wrote:
> > In general, using floating point values with time is an
> > incredibly bad idea. It can certainly make sense when printing
> > stuff out, but using it in calculations is just asking for
> > trouble given all of the unnecessary imprecision that it adds.
> > So, Duration does not directly support floating point values at
> > all, and that's very much on purpose. I'd strongly argue that
> > the fact that TickDuration does was a mistake.
> >
> > So, if you're doing floating point calculations with time, I'd
> > strongly urge you to rethink your code. And if you're just
> > trying to print out the a duration as a floating point value,
> > because it's nice to view that way, then that's fine, but
> > you'll need to do the conversion yourself. And it's not that
> > hard. It just isn't handed to you directly, because aside from
> > printing, code really shouldn't be using floating point values
> > for time. e.g.
> >
> > string toFloatingSeconds(Duration d)
> > {
> > import std.conv;
> > enum hnsecsPerSecond = convert!("seconds", "hnsecs")(1);
> > auto s = d.split!("seconds", "hnsecs")();
> > return to!string(s.seconds + cast(real)(s.hnsecs) /
> > hnsecsPerSecond);
> > }
> >
> > And yes, that's a bit more of a pain than using to!("seconds",
> > float) with TickDuration, but it's also the sort of thing that
> > most code really shouldn't be doing. So, adding that
> > functionality to Duration would just encourage folks to write
> > buggy code.
> >
> > - Jonathan M Davis
>
> I want to use float time in a game where I call the update method
> passing the delta time as float seconds. It's more easy to
> multiply the dt with a speed constant meaning how much the object
> will move after 1 second. Such float delta time is used in many
> game engines and it's somewhat standart way of doing it. Also the
> method you wrote returns a string and I need a float to multiply
> it with a number.
> Thanks for the reply anyway
Using floating point as a delta for time is inherently buggy. Depending on
what you're doing, you may get away with it, but it means that error is
going to creep into your timing. And the bugs introduced by using floating
point like that can be quite subtle. I would strongly urge anyone using
floating point values with timing like that to rework their code to use
integral values. Aside from TickDuration, all of core.time and std.datetime
quite carefully avoids floating point values - even functions like
convClockFreq (which converts one clock frequency to another).
So, if you want to use floating point values with time stuff, that's
obviously your prerogative, but Duration does not directly support it and
isn't ever going to directly support it precisely because it's error-prone.
- Jonathan M Davis
Re: core.time Duration how to get units in double/float format?
On Tuesday, 19 January 2016 at 15:25:58 UTC, wobbles wrote: On Tuesday, 19 January 2016 at 14:07:50 UTC, Borislav Kosharov wrote: On Monday, 18 January 2016 at 12:46:31 UTC, Jonathan M Davis wrote: [...] I want to use float time in a game where I call the update method passing the delta time as float seconds. It's more easy to multiply the dt with a speed constant meaning how much the object will move after 1 second. Such float delta time is used in many game engines and it's somewhat standart way of doing it. Also the method you wrote returns a string and I need a float to multiply it with a number. Thanks for the reply anyway Checkout out how DSFML handles this. You simply pass around a Clock object that you can restart every frame using clock.restart(); You then call your update function with update(Clock.getElapsedTime()); Then in each objects update(Time t) method you just get the time in whatever unit you want. Works pretty well. http://www.dsfml.com/ Yes that's exactly what I'm using. But they changed it to return a Duration instead of Time and that broke my code. See the source https://github.com/Jebbs/DSFML/blob/master/src/dsfml/system/clock.d#L65
Re: core.time Duration how to get units in double/float format?
On Monday, 18 January 2016 at 12:46:31 UTC, Jonathan M Davis
wrote:
In general, using floating point values with time is an
incredibly bad idea. It can certainly make sense when printing
stuff out, but using it in calculations is just asking for
trouble given all of the unnecessary imprecision that it adds.
So, Duration does not directly support floating point values at
all, and that's very much on purpose. I'd strongly argue that
the fact that TickDuration does was a mistake.
So, if you're doing floating point calculations with time, I'd
strongly urge you to rethink your code. And if you're just
trying to print out the a duration as a floating point value,
because it's nice to view that way, then that's fine, but
you'll need to do the conversion yourself. And it's not that
hard. It just isn't handed to you directly, because aside from
printing, code really shouldn't be using floating point values
for time. e.g.
string toFloatingSeconds(Duration d)
{
import std.conv;
enum hnsecsPerSecond = convert!("seconds", "hnsecs")(1);
auto s = d.split!("seconds", "hnsecs")();
return to!string(s.seconds + cast(real)(s.hnsecs) /
hnsecsPerSecond);
}
And yes, that's a bit more of a pain than using to!("seconds",
float) with TickDuration, but it's also the sort of thing that
most code really shouldn't be doing. So, adding that
functionality to Duration would just encourage folks to write
buggy code.
- Jonathan M Davis
I want to use float time in a game where I call the update method
passing the delta time as float seconds. It's more easy to
multiply the dt with a speed constant meaning how much the object
will move after 1 second. Such float delta time is used in many
game engines and it's somewhat standart way of doing it. Also the
method you wrote returns a string and I need a float to multiply
it with a number.
Thanks for the reply anyway
Re: core.time Duration how to get units in double/float format?
On Tuesday, 19 January 2016 at 14:07:50 UTC, Borislav Kosharov wrote: On Monday, 18 January 2016 at 12:46:31 UTC, Jonathan M Davis wrote: [...] I want to use float time in a game where I call the update method passing the delta time as float seconds. It's more easy to multiply the dt with a speed constant meaning how much the object will move after 1 second. Such float delta time is used in many game engines and it's somewhat standart way of doing it. Also the method you wrote returns a string and I need a float to multiply it with a number. Thanks for the reply anyway Checkout out how DSFML handles this. You simply pass around a Clock object that you can restart every frame using clock.restart(); You then call your update function with update(Clock.getElapsedTime()); Then in each objects update(Time t) method you just get the time in whatever unit you want. Works pretty well. http://www.dsfml.com/
Re: core.time Duration how to get units in double/float format?
On Sunday, January 17, 2016 14:43:26 Borislav Kosharov via Digitalmars-d-learn
wrote:
> Seeing that TickDuration is being deprecated and that I should
> use Duration instead, I faced a problem. I need to get total
> seconds like a float. Using .total!"seconds" returns a long and
> if the duration is less than 1 second I get 0. My question is
> whats the right way to do it. Because I saw that TickDuration has
> a to!("seconds", float) method, but Duration doesn't have one. I
> can convert Duration to TickDuration and call to but seeing that
> its deprecated makes me think there is a better way.
In general, using floating point values with time is an incredibly bad idea.
It can certainly make sense when printing stuff out, but using it in
calculations is just asking for trouble given all of the unnecessary
imprecision that it adds. So, Duration does not directly support floating
point values at all, and that's very much on purpose. I'd strongly argue
that the fact that TickDuration does was a mistake.
So, if you're doing floating point calculations with time, I'd strongly urge
you to rethink your code. And if you're just trying to print out the a
duration as a floating point value, because it's nice to view that way, then
that's fine, but you'll need to do the conversion yourself. And it's not
that hard. It just isn't handed to you directly, because aside from
printing, code really shouldn't be using floating point values for time.
e.g.
string toFloatingSeconds(Duration d)
{
import std.conv;
enum hnsecsPerSecond = convert!("seconds", "hnsecs")(1);
auto s = d.split!("seconds", "hnsecs")();
return to!string(s.seconds + cast(real)(s.hnsecs) / hnsecsPerSecond);
}
And yes, that's a bit more of a pain than using to!("seconds", float) with
TickDuration, but it's also the sort of thing that most code really
shouldn't be doing. So, adding that functionality to Duration would just
encourage folks to write buggy code.
- Jonathan M Davis
Re: core.time Duration how to get units in double/float format?
On Sunday, 17 January 2016 at 18:57:13 UTC, biozic wrote:
On Sunday, 17 January 2016 at 14:43:26 UTC, Borislav Kosharov
wrote:
Seeing that TickDuration is being deprecated and that I should
use Duration instead, I faced a problem. I need to get total
seconds like a float. Using .total!"seconds" returns a long
and if the duration is less than 1 second I get 0. My question
is whats the right way to do it. Because I saw that
TickDuration has a to!("seconds", float) method, but Duration
doesn't have one. I can convert Duration to TickDuration and
call to but seeing that its deprecated makes me think there is
a better way.
Why not just use a smaller granularity for Duration.total and
convert the result?
duration.total!"nsecs" / cast(float) 1e9
Yea I could do that, but its not intuitive to get a total of one
magnitude to just convert it to another. My question is why
doesn't `to!` accept Duration.
Re: core.time Duration how to get units in double/float format?
On Sunday, 17 January 2016 at 14:43:26 UTC, Borislav Kosharov
wrote:
Seeing that TickDuration is being deprecated and that I should
use Duration instead, I faced a problem. I need to get total
seconds like a float. Using .total!"seconds" returns a long and
if the duration is less than 1 second I get 0. My question is
whats the right way to do it. Because I saw that TickDuration
has a to!("seconds", float) method, but Duration doesn't have
one. I can convert Duration to TickDuration and call to but
seeing that its deprecated makes me think there is a better way.
Why not just use a smaller granularity for Duration.total and
convert the result?
duration.total!"nsecs" / cast(float) 1e9
core.time Duration how to get units in double/float format?
Seeing that TickDuration is being deprecated and that I should
use Duration instead, I faced a problem. I need to get total
seconds like a float. Using .total!"seconds" returns a long and
if the duration is less than 1 second I get 0. My question is
whats the right way to do it. Because I saw that TickDuration has
a to!("seconds", float) method, but Duration doesn't have one. I
can convert Duration to TickDuration and call to but seeing that
its deprecated makes me think there is a better way.
