'using namespace std;' in header files can conflict with custom
namespace names. For example 'string' is used without 'std::'
qualification. If tz.h is included in a file where string is a
namespace, it cannot be compiled anymore. The same happens with date.h
if ONLY_C_LOCALE=1.
Implemented clock_time_conversion<D, local_t> calling D::from_local
and clock_time_conversion<locat_t, S> calling S::to_local.
To avoid ambiguities addes:
* clock_time_conversion<local_t, local_t> - idenitity
* clock_time_conversion<local_t, utc_clock> - same as default (utc_clock::to_local)
* clock_time_conversion<utc_clock, local_t> - same as default (utc_clock::from_local)
In addition, as std::chrono::system_clock cannot be edited, added:
* clock_time_conversion<local_t, std::chrono::system_clock> - assumes same epoch
* clock_time_conversion<std::chrono::system_clock, local_t> - assumes same epoch
They will be required to resolve amibiguity anyway.
Implemented to_local and from_local functions for utc_clock,
tai_clock and gps_clock. For the tai/gps clock used this function
for defining the io - we delegate to serializing/parsing local
time.
The drwaback is that the local_time cannot properly represent
leap second in the UTC time, so separate serialization is needed.
* There has been a great deal of anguish over the encoding of
weekdays: whether [0, 6] maps to [Sunday, Saturday] or
[1, 7] maps to [Monday, Sunday]. This commit attempts
to address that issue, but will break a small amount of
code at compile-time. See below on how to fix that.
* The weekday constructor used to accept [0, 6] to represent
[Sunday, Saturday]. It now accepts [0, 7] to represent
[Sunday, Saturday] with both 0 and 7 mapping to Sunday.
* The conversion from weekday to unsigned has been removed.
* To convert a weekday to unsigned replace:
auto u = unsigned{wd};
with:
auto u = (wd - Sunday).count();
This maps [Sunday, Saturday] to [0, 6], which is the
C/POSIX mapping. If you prefer the ISO mapping
([Monday, Sunday] -> [1, 7]), then do:
auto u = (wd - Monday).count() + 1;
* Added new overloads for operator+/- between year_month and duration
that is convertible to years, so it is better candidate for operands
that are convertible to both years and months. To preserve
functionality, this operator is conditionally noexcept.
* Reworked year_month_day, year_month_day_last, year_month_weekday,
and year_month_weekday_last.
* Added tests for this new functionality.
