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The class ti(time_point) is defined in the tt(std::chrono) namespace.
Objects of the class tt(std::chrono::time_point) define a point in time.
Before using the class tt(std::chrono::time_point) the tthi(chrono) header
file must be included.
The class tt(time_point) is a class template, requiring two template type
arguments: a tt(Clock) type and a tt(Duration) type. The tt(Clock) type
usually is one of the predefined clock types, e.g.,
tt(chrono::system_clock). The tt(Duration) type may be omitted, in which case
the tt(Clock's duration) type is used. An explicit tt(duration) type may also
be provided.
In the previous section tt(auto) was used to specify the type of the return
value of tt(system_clock::now). The explicit definition looks like this:
verb(
std::chrono::time_point<std::chrono::system_clock> now =
std::chrono::system_clock::now();
)
The class tt(std::chrono::time_point) features three constructors:
itemization(
ittq(time_point())
(the default constructor represents the beginning of the clock's
emi(epoch) (E.g., Jan, 1, 1970, 00:00h);)
ittq(time_point(time_point<Clock, Duration> const &timeStep))
(initializes a tt(time_point) object to represent a point in time
tt(timeStep Duration) units byond the clock's epoch;)
ittq(time_point(time_point<Clock, Duration2> const &timeStep))
(this constructor is defined as a member template, using the template
header tt(template <typename Duration2>). The type tt(Duration2) is a
tt(std::chrono::duration) (or comparable) type, using a possibly larger period
for its unit than tt(time_point's Duration) type. It initializes a
tt(time_point) object to represent a point in time tt(timeStep Duration2)
units byond the clock's epoch.)
)
The class tt(std::chrono::time_point) has these operators and members:
itemization(
ittq(std::chrono::time_point &operator+=(Duration const &duration))
(this operator is also available as binary arithmetic
operator,linebreak()
expecting a tt(std::chrono::time_point const &) and a tt(Duration
const &) argument (in any order). The amount of time represented by
tt(duration) is added to the current tt(time_point) value. Example:
verb(
std::chrono::system_clock::now() + seconds(5);
)
)
ittq(std::chrono::time_point &operator-=(Duration const &duration))
(this operator is also available as binary arithmetic
operator,linebreak()
expecting a tt(std::chrono::time_point const &) and a tt(Duration
const &) argument (in any order). The amount of time represented by
tt(duration) is subtracted from the current tt(time_point)
value. Example:
verb(
auto point = std::chrono::system_clock::now();
point -= seconds(5);
)
)
ithtq(time_since_epoch)(constexpr Duration time_since_epoch() const)
(returns the object's tt(Duration) since the epoch.)
ithtq(min)(static constexpr time_point min())
(a static member returning the value returned by the time point's
tt(duration::min) value.)
ithtq(max)(static constexpr time_point max())
(a static member returning the value returned by the time point's
tt(duration::max) value.)
)
All predefined clocks use nanoseconds as their time unit. To obtain the
time expressed in a larger time unit, divide the value returned by the
tt(time_point's count) value by larger time unit
converted to nanoseconds. E.g., the number of hours passed since the beginning
of the epoch is:
verb(
using namespace std;
using namespace chrono; // for brevity
cout << system_clock::now().time_since_epoch().count() /
nanoseconds(hours(1)).count() << " hours since the epoch\n";
)
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