Topic: Encapsulate std::tm in std::chrono::time_point<>
Author: Howard Hinnant <howard.hinnant@gmail.com>
Date: Mon, 29 Aug 2016 18:05:53 -0400
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On Aug 29, 2016, at 5:54 PM, HarD Gamer <rodrigojose690@gmail.com> wrote:
>
>
>
> Now, if we need a textual representation of a time_point or the current hour, we have a lot of work to do.
> If we had a intuitive time_point<...> now; .... now.sec(); now.min(); now.hour(); now.day(); now.month(); now.year(); ... [or now.tm()].
> the work would be more readably and fun.
> And what about a simple now.to_string()?
How do you feel about this:
#include "tz.h"
#include <iostream>
int
main()
{
using namespace date;
using namespace std;
using namespace std::chrono_literals;
auto ineedhours3 = make_zoned(current_zone(),
floor<chrono::seconds>(chrono::system_clock::now()));
cout << "The time is " << format("%a %b %d %T %Y\n", ineedhours3);
auto lt = ineedhours3.get_local_time();
auto h = make_time(lt - floor<days>(lt)).hours();
if (h > 18h)
cout << "Let's to party!!\n";
else
cout << "The party is comming..\n";
}
?
https://github.com/HowardHinnant/date
Howard
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.
Author: =?UTF-8?Q?Jos=C3=A9_Rodrigo?= <rodrigojose690@gmail.com>
Date: Mon, 29 Aug 2016 19:07:42 -0300
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good man
2016-08-29 19:05 GMT-03:00 Howard Hinnant <howard.hinnant@gmail.com>:
> On Aug 29, 2016, at 5:54 PM, HarD Gamer <rodrigojose690@gmail.com> wrote:
> >
> >
> >
> > Now, if we need a textual representation of a time_point or the current
> hour, we have a lot of work to do.
> > If we had a intuitive time_point<...> now; .... now.sec(); now.min();
> now.hour(); now.day(); now.month(); now.year(); ... [or now.tm()].
> > the work would be more readably and fun.
> > And what about a simple now.to_string()?
>
> How do you feel about this:
>
> #include "tz.h"
> #include <iostream>
>
> int
> main()
> {
> using namespace date;
> using namespace std;
> using namespace std::chrono_literals;
> auto ineedhours3 = make_zoned(current_zone(),
> floor<chrono::seconds>(chrono:
> :system_clock::now()));
> cout << "The time is " << format("%a %b %d %T %Y\n", ineedhours3);
> auto lt = ineedhours3.get_local_time();
> auto h = make_time(lt - floor<days>(lt)).hours();
> if (h > 18h)
> cout << "Let's to party!!\n";
> else
> cout << "The party is comming..\n";
> }
>
> ?
>
> https://github.com/HowardHinnant/date
>
> Howard
>
> --
> You received this message because you are subscribed to the Google Groups
> "ISO C++ Standard - Future Proposals" group.
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> isocpp.org/d/msgid/std-proposals/A87786B6-D6E5-4E97-
> A393-0E77D4583CE5%40gmail.com.
>
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<div dir=3D"ltr">good man</div><div class=3D"gmail_extra"><br><div class=3D=
"gmail_quote">2016-08-29 19:05 GMT-03:00 Howard Hinnant <span dir=3D"ltr">&=
lt;<a href=3D"mailto:howard.hinnant@gmail.com" target=3D"_blank">howard.hin=
nant@gmail.com</a>></span>:<br><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span cl=
ass=3D"">On Aug 29, 2016, at 5:54 PM, HarD Gamer <<a href=3D"mailto:rodr=
igojose690@gmail.com">rodrigojose690@gmail.com</a>> wrote:<br>
><br>
><br>
><br>
> Now, if we need a textual representation of a time_point or the curren=
t hour, we have a lot of work to do.<br>
> If we had a intuitive=C2=A0 time_point<...> now; .... now.sec();=
now.min(); now.hour(); now.day(); now.month(); now.year(); ... [or <a href=
=3D"http://now.tm" rel=3D"noreferrer" target=3D"_blank">now.tm</a>()].<br>
> the work would be more readably and fun.<br>
> And what about a simple now.to_string()?<br>
<br>
</span>How do you feel about this:<br>
<br>
=C2=A0 =C2=A0 #include "tz.h"<br>
=C2=A0 =C2=A0 #include <iostream><br>
<br>
=C2=A0 =C2=A0 int<br>
=C2=A0 =C2=A0 main()<br>
=C2=A0 =C2=A0 {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace date;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace std;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace std::chrono_literals;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto ineedhours3 =3D make_zoned(current_zone(),=
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 floor<chrono=
::seconds>(chrono:<wbr>:system_clock::now()));<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "The time is " <<=
format("%a %b %d %T %Y\n", ineedhours3);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto lt =3D ineedhours3.get_local_time();<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto h =3D make_time(lt - floor<days>(lt)=
).hours();<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if (h > 18h)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "Let's to =
party!!\n";<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 else<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "The party is =
comming..\n";<br>
=C2=A0 =C2=A0 }<br>
<br>
?<br>
<br>
<a href=3D"https://github.com/HowardHinnant/date" rel=3D"noreferrer" target=
=3D"_blank">https://github.com/<wbr>HowardHinnant/date</a><br>
<br>
Howard<br>
<span class=3D""><br>
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</blockquote></div><br></div>
<p></p>
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Author: Tony V E <tvaneerd@gmail.com>
Date: Mon, 29 Aug 2016 18:14:22 -0400
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I'm still confused (although maybe it is all the 'auto's such that I don't
know what is what)
see below:
On Mon, Aug 29, 2016 at 6:05 PM, Howard Hinnant <howard.hinnant@gmail.com>
wrote:
>
> How do you feel about this:
>
> #include "tz.h"
> #include <iostream>
>
> int
> main()
> {
> using namespace date;
> using namespace std;
> using namespace std::chrono_literals;
> auto ineedhours3 = make_zoned(current_zone(),
> floor<chrono::seconds>(chrono:
> :system_clock::now()));
> cout << "The time is " << format("%a %b %d %T %Y\n", ineedhours3);
>
OK, it seems like ineedhours3 is some type of timey-wimey thing that has
what I need (ie hours).
Why do I need these next two lines:
> auto lt = ineedhours3.get_local_time();
> auto h = make_time(lt - floor<days>(lt)).hours();
>
In particular, make_time()? Ain't nobody got time for that. Didn't I
already have a time thing? It also looks like magic. floor<days>...
> if (h > 18h)
> cout << "Let's to party!!\n";
> else
> cout << "The party is comming..\n";
> }
>
> ?
>
> https://github.com/HowardHinnant/date
>
> Howard
>
>
--
Be seeing you,
Tony
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<div dir=3D"ltr"><div>I'm still confused (although maybe it is all the =
'auto's such that I don't know what is what)<br></div>see below=
:<br><div><div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On=
Mon, Aug 29, 2016 at 6:05 PM, Howard Hinnant <span dir=3D"ltr"><<a href=
=3D"mailto:howard.hinnant@gmail.com" target=3D"_blank">howard.hinnant@gmail=
..com</a>></span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"ma=
rgin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=3D=
""><br>
</span>How do you feel about this:<br>
<br>
=C2=A0 =C2=A0 #include "tz.h"<br>
=C2=A0 =C2=A0 #include <iostream><br>
<br>
=C2=A0 =C2=A0 int<br>
=C2=A0 =C2=A0 main()<br>
=C2=A0 =C2=A0 {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace date;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace std;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 using namespace std::chrono_literals;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto ineedhours3 =3D make_zoned(current_zone(),=
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 floor<chrono=
::seconds>(chrono:<wbr>:system_clock::now()));<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "The time is " <<=
format("%a %b %d %T %Y\n", ineedhours3);<br></blockquote><div><b=
r></div><div>OK, it seems like ineedhours3 is some type of timey-wimey thin=
g that has what I need (ie hours).<br></div><div>Why do I need these next t=
wo lines:<br>=C2=A0<br></div><blockquote class=3D"gmail_quote" style=3D"mar=
gin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto lt =3D ineedhours3.get_local_time();<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 auto h =3D make_time(lt - floor<days>(lt)=
).hours();<br></blockquote><div><br></div><div>In particular, make_time()? =
Ain't nobody got time for that. Didn't I already have a time thing?=
=C2=A0 It also looks like magic. floor<days>...<br></div><div>=C2=A0<=
/div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-le=
ft:1px #ccc solid;padding-left:1ex">
=C2=A0 =C2=A0 =C2=A0 =C2=A0 if (h > 18h)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "Let's to =
party!!\n";<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 else<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 cout << "The party is =
comming..\n";<br>
=C2=A0 =C2=A0 }<br>
<br>
?<br>
<br>
<a href=3D"https://github.com/HowardHinnant/date" rel=3D"noreferrer" target=
=3D"_blank">https://github.com/<wbr>HowardHinnant/date</a><br>
<br>
Howard<br>
<span class=3D""></span><br></blockquote></div><br clear=3D"all"><br>-- <br=
><div class=3D"gmail_signature" data-smartmail=3D"gmail_signature"><div dir=
=3D"ltr"><div>Be seeing you,<br></div>Tony<br></div></div>
</div></div></div></div>
<p></p>
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.
Author: Howard Hinnant <howard.hinnant@gmail.com>
Date: Mon, 29 Aug 2016 18:29:15 -0400
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On Aug 29, 2016, at 6:14 PM, Tony V E <tvaneerd@gmail.com> wrote:
>=20
> I'm still confused (although maybe it is all the 'auto's such that I don'=
t know what is what)
> see below:
Fortunately there are docs:
https://howardhinnant.github.io/date/tz.html
https://howardhinnant.github.io/date/date.html
(not that you should=E2=80=99ve run out and immediately read and understood=
all that, just giving handy links)
>=20
>> On Mon, Aug 29, 2016 at 6:05 PM, Howard Hinnant <howard.hinnant@gmail.co=
m> wrote:
>>=20
>> How do you feel about this:
>>=20
>> #include "tz.h"
>> #include <iostream>
>>=20
>> int
>> main()
>> {
>> using namespace date;
>> using namespace std;
>> using namespace std::chrono_literals;
>> auto ineedhours3 =3D make_zoned(current_zone(),
>> floor<chrono::seconds>(chrono::sys=
tem_clock::now()));
>> cout << "The time is " << format("%a %b %d %T %Y\n", ineedhours3=
);
>>=20
> OK, it seems like ineedhours3 is some type of timey-wimey thing that has =
what I need (ie hours).
> Why do I need these next two lines:
The type of ineedhours3 is a a zoned_time<seconds>, also known as zoned_sec=
onds for short.
https://howardhinnant.github.io/date/tz.html#zoned_time
A zoned_time is a pairing of a time_zone and local_time. Or you can equiva=
lently think of it as a pairing of a time_zone and a sys_time. Either way,=
it represents a well-specified time in some time zone. From it you can ge=
t the local time, the UTC time and the time zone. And you can also format =
it (including %Z (time zone abbreviation) and %z (time zone offset).
>=20
>> auto lt =3D ineedhours3.get_local_time();
>> auto h =3D make_time(lt - floor<days>(lt)).hours();
>>=20
> In particular, make_time()? Ain't nobody got time for that. Didn't I alre=
ady have a time thing? It also looks like magic. floor<days>=E2=80=A6
lt has type local_time<seconds>, or local_seconds for short. local_time is=
a std::chrono::time_point that is not associated with _any_ time zone. On=
e can think of it as the void* of chrono::time_points.
floor<Duration>(time_point) is actually already in the C++1z working draft.=
It takes a time_point of a finer duration and truncates it to a time_poin=
t of a coarser duration. In this case the finer duration is seconds, and t=
he coarser duration is days. days is a chrono::duration<int, ratio<86400>>=
..
The expression =E2=80=9Clt - floor<days>(lt)=E2=80=9D converts a time_point=
since whatever epoch into a chrono::duration of the time since midnight. =
Since lt has type local_time, as opposed to being a system_clock::time_poin=
t, this is with respect to local midnight, as opposed to midnight UTC. We =
could have just as easily gotten time since UTC midnight by extracting inee=
dhours3.get_sys_time(), resulting in a system_clock::time_point with second=
s precision, or sys_seconds for short.
make_time takes a chrono::duration and breaks it down into a {hours, minute=
s, seconds} struct. It has a .hours() getter to get the hours. The type o=
f that result is chrono::hours.
>=20
>> if (h > 18h)
>> cout << "Let's to party!!\n";
>> else
>> cout << "The party is comming..\n";
>> }
>>=20
>> ?
>>=20
>> https://github.com/HowardHinnant/date
>>=20
Howard
--=20
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Author: Howard Hinnant <howard.hinnant@gmail.com>
Date: Mon, 29 Aug 2016 20:05:21 -0400
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On Aug 29, 2016, at 6:29 PM, Howard Hinnant <howard.hinnant@gmail.com> wrot=
e:
>=20
>>> auto h =3D make_time(lt - floor<days>(lt)).hours();
>>>=20
>> In particular, make_time()? Ain't nobody got time for that. Didn't I alr=
eady have a time thing? It also looks like magic. floor<days>=E2=80=A6
>=20
> make_time takes a chrono::duration and breaks it down into a {hours, minu=
tes, seconds} struct. It has a .hours() getter to get the hours. The type =
of that result is chrono::hours.
On further reflection, make_time() really is overkill for this application =
since the minutes and seconds are discarded. The following is both simpler=
and slightly more efficient:
auto h =3D floor<chrono::hours>(lt - floor<days>(lt));
Howard
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