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Rename day_point to sys_days

Howard Hinnant
2016-05-21 11:13:46 -04:00
parent 2df87145c3
commit 813a75305c
1 changed files with 27 additions and 28 deletions
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55
Examples-and-Recipes.md

@@ -29,7 +29,7 @@ int y=2015, m=7, d=30, h=12, min=34, s=56;
auto ymd = year(y)/m/d; // Yields a year_month_day type
if (!ymd.ok())
throw std::runtime_error("Invalid date");
system_clock::time_point = day_point(ymd) +
system_clock::time_point tp = sys_days(ymd) +
hours(h) + minutes(min) + seconds(s);
```
@@ -47,7 +47,7 @@ void to_time_point(const std::tm& t,
auto ymd = year(y)/(t.tm_mon+1)/t.tm_mday; // Yields a year_month_day type
if (!ymd.ok())
throw std::runtime_error("Invalid date");
tp = day_point(ymd) +
tp = sys_days(ymd) +
hours(t.tm_hour) + minutes(t.tm_min) + seconds(t.tm_sec);
}
@@ -87,10 +87,9 @@ std::tm to_calendar_time(std::chrono::time_point<Clock, Duration> tp)
auto ymd = year_month_day(date);
auto weekday = year_month_weekday(date).weekday_indexed().weekday();
auto tod = make_time(tp - date);
days daysSinceJan1 = date - day_point(ymd.year()/1/1);
days daysSinceJan1 = date - sys_days(ymd.year()/1/1);
std::tm result;
std::memset(&result, 0, sizeof(result));
std::tm result{};
result.tm_sec = tod.seconds().count();
result.tm_min = tod.minutes().count();
result.tm_hour = tod.hours().count();
@@ -119,7 +118,7 @@ The following function will "normalize" a `year_month_day`, much like `mktime` n
{
using namespace date;
ymd += months{0};
ymd = day_point(ymd);
ymd = sys_days{ymd};
return ymd;
}
@@ -127,11 +126,11 @@ The first line simply adds 0 months to the `ymd`. If `ymd.month()` is 0, this w
The second line will "normalize" the day field. The second line requires that the month field is already normalized. For example `2015_y/dec/32` will become `2016_y/jan/1`. If the day field is already in range, there will be no change.
The conversion from `year_month_day` to `day_point` calls this algorithm:
The conversion from `year_month_day` to `sys_days` calls this algorithm:
http://howardhinnant.github.io/date_algorithms.html#days_from_civil
And the conversion from `day_point` back to `year_month_day` calls this algorithm:
And the conversion from `sys_days` back to `year_month_day` calls this algorithm:
http://howardhinnant.github.io/date_algorithms.html#civil_from_days
@@ -145,7 +144,7 @@ Example:
std::cout << ymd << (ymd.ok() ? "\n" : " invalid date\n");
ymd += months{0};
std::cout << ymd << (ymd.ok() ? "\n" : " invalid date\n");
ymd = day_point(ymd);
ymd = sys_days{ymd};
std::cout << ymd << (ymd.ok() ? "\n" : " invalid date\n");
}
@@ -181,10 +180,10 @@ Here is a function to perform that conversion:
{
using namespace date;
using namespace std::chrono;
auto utc = utc_clock::sys_to_utc(day_point{y/jan/1}) + us;
auto utc = utc_clock::sys_to_utc(sys_days{y/jan/1}) + us;
auto sys = utc_clock::utc_to_sys(utc);
auto dp = floor<days>(sys);
auto d = dp - day_point{1958_y/jan/1};
auto d = dp - sys_days{1958_y/jan/1};
us = utc - utc_clock::sys_to_utc(dp);
auto ms = duration_cast<milliseconds>(us);
us -= ms;
@@ -226,12 +225,12 @@ This creates two `year_month` objects and subtracts them. This gives a `std::ch
36
To include the influence of the day-fields, it is best to convert `d1` and `d2` to `day_point`s:
To include the influence of the day-fields, it is best to convert `d1` and `d2` to `sys_days `s:
auto dp1 = day_point(d1);
auto dp2 = day_point(d2);
auto dp1 = sys_days(d1);
auto dp2 = sys_days(d2);
Now we could (for example) subtract the two `day_point`s, and round the result to the nearest integral month:
Now we could (for example) subtract the two `sys_days `s, and round the result to the nearest integral month:
std::cout << round<months>(dp2-dp1).count() << '\n';
@@ -260,11 +259,11 @@ The [ISO week date](https://en.wikipedia.org/wiki/ISO_week_date) is an internati
Like `<date.h>`, you can specify an ISO week date in any of the three orders: y/wn/wd, wd/wn/y, wn/wd/y (big endian, little endian, mixed (american) endian).
Also like `<date.h>`, you can implicitly convert a ISO week date to `day_point`, and vice-versa. For convenience, an alias of `date::day_point` exists as `iso_week::day_point`:
Also like `<date.h>`, you can implicitly convert a ISO week date to `sys_days `, and vice-versa. For convenience, an alias of `date:: sys_days ` exists as `iso_week:: sys_days `:
iso_week::day_point dp = iso_date;
iso_week:: sys_days dp = iso_date;
And recall that `day_point` is just a type alias for a `std::chrono::time_point<std::chrono::system_clock, days>`. So the ISO week date (`iso_week:year_weeknum_weekday`) is immediately interoperable with the entire `<chrono>` library, just like `date::year_month_day` is.
And recall that `sys_days ` is just a type alias for a `std::chrono::time_point<std::chrono::system_clock, days>`. So the ISO week date (`iso_week:year_weeknum_weekday`) is immediately interoperable with the entire `<chrono>` library, just like `date::year_month_day` is.
auto now = std::chrono::system_clock::now();
auto dp = date::floor<iso_week::days>(now);
@@ -276,7 +275,7 @@ Which just output for me:
2016-W11-Sat 03:07:02.460737
And because `iso_week:year_weeknum_weekday` is implicitly convertible to and from `day_point`, that makes it immediately (and explicitly) convertible to any other calendar system that is implicitly convertible to and from `day_point`:
And because `iso_week:year_weeknum_weekday` is implicitly convertible to and from `sys_days `, that makes it immediately (and explicitly) convertible to any other calendar system that is implicitly convertible to and from `sys_days `:
auto civil_date = date::year_month_day{iso_date};
std::cout << civil_date << ' ' << time << '\n';
@@ -285,7 +284,7 @@ which outputs:
2016-03-19 03:07:02.460737
And there you have it: `day_point` is a _Rosetta Stone_ for translating _any_ calendar to any other calendar. Just make your calendar convert to and from `day_point`, and you have interoperability with _every_ other calendar which does so.
And there you have it: `sys_days ` is a _Rosetta Stone_ for translating _any_ calendar to any other calendar. Just make your calendar convert to and from `sys_days `, and you have interoperability with _every_ other calendar which does so.
using namespace date::literals;
auto today = 2016_y/mar/19;
@@ -301,7 +300,7 @@ Output:
Coptic : 1732-07-10
iso_week: 2016-W11-Sat
This is somewhat of a teaser because as I write this the Julian and Coptic calendars aren't publicly available yet. The software exists, but is not fully tested yet. But more importantly, just follow the recipe in `<iso_week.h>` for your favorite calendar (convert to and from `day_point`), and your calendar is now part of the club! Contribute your calendar so we can all use it!
This is somewhat of a teaser because as I write this the Julian and Coptic calendars aren't publicly available yet. The software exists, but is not fully tested yet. But more importantly, just follow the recipe in `<iso_week.h>` for your favorite calendar (convert to and from `sys_days`), and your calendar is now part of the club! Contribute your calendar so we can all use it!
<a name="birthday2gs"></a>
### 2Gs Birthday
@@ -321,7 +320,7 @@ This example demonstrates both some simple date arithmetic, and how to handle di
using namespace date;
// Dave was born April 24, 1954. 10:03 AM pst
// Want to know when he is 2 Gigaseconds old
auto birth = day_point{apr/24/1954} + 10h + 3min;
auto birth = sys_days{apr/24/1954} + 10h + 3min;
auto z = locate_zone("America/Los_Angeles");
auto t = z->to_sys(birth);
t += 2'000'000'000s;
@@ -353,12 +352,12 @@ An [ordinal date](https://en.wikipedia.org/wiki/Ordinal_date) consists of a year
// calculating the year and the day of the year
const auto year = ymd.year();
const auto year_day = daypoint - day_point{year/jan/0};
const auto year_day = daypoint - sys_days{year/jan/0};
std::cout << year << '-' << std::setfill('0') << std::setw(3) << year_day.count() << std::endl;
// inverse calculation and check
assert(ymd == year_month_day{day_point{year/jan/0} + year_day});
assert(ymd == year_month_day{sys_days{year/jan/0} + year_day});
}
<a name="tz_search"></a>
@@ -378,8 +377,8 @@ Let's say you want to search the globe, and all time, for time zones when the da
auto& db = get_tzdb();
for (auto const& z : db.zones)
{
auto begin = day_point{jan/1/year::min()} + 0s;
auto end = day_point{jan/1/2035} + 0s;
auto begin = sys_days{jan/1/year::min()} + 0s;
auto end = sys_days{jan/1/2035} + 0s;
do
{
auto info = z.get_info(begin, tz::utc);
@@ -444,8 +443,8 @@ Ever wonder how the global use of daylight saving time is trending with time? H
for (auto& z : db.zones)
{
++total;
auto info1 = z.get_info(day_point{y/jan/15}, tz::utc);
auto info2 = z.get_info(day_point{y/jul/15}, tz::utc);
auto info1 = z.get_info(sys_days{y/jan/15}, tz::utc);
auto info2 = z.get_info(sys_days{y/jul/15}, tz::utc);
if (info1.save != 0min || info2.save != 0min)
++use_daylight;
}