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Defined in header <chrono> | ||
constexprbool is_am(conststd::chrono::hours& h)noexcept; | (1) | (since C++20) |
constexprbool is_pm(conststd::chrono::hours& h)noexcept; | (2) | (since C++20) |
constexprstd::chrono::hours make12(conststd::chrono::hours& h)noexcept; | (3) | (since C++20) |
constexprstd::chrono::hours make24(conststd::chrono::hours& h, bool is_pm)noexcept; | (4) | (since C++20) |
These functions aid in translating between a 12-hour format time of day, and a 24-hour format time of day.
| h | - | 12-hour or 24-hour format time to detect |
| is_pm | - | whether the 12-hour format time is p.m. |
[0h, 23h], returns the 12-hour equivalent in range[1h, 12h]. Otherwise, the return value is unspecified.[1h, 12h], returns the 24-hour equivalent in range[0h, 11h] ifis_pm isfalse, or in range[12h, 23h] otherwise. Otherwise, the return value is unspecified.#include <chrono>#include <iomanip>#include <iostream>#include <utility> int main(){usingnamespace std::chrono; static_assert( is_am(10h)&& is_am(11h)&&!is_am(12h)&&!is_am(23h)&&!is_pm(10h)&&!is_pm(11h)&& is_pm(12h)&& is_pm(23h)); std::cout<<"make12():\n"; for(const hours hh:{0h, 1h, 11h, 12h, 13h, 23h}){const hours am{make12(hh)};std::cout<<std::setw(2)<< hh.count()<<"h == "<<std::setw(2)<< am.count()<<(is_am(hh)?"h a.m.\n":"h p.m.\n");} std::cout<<"\nmake24():\n"; using p=std::pair<hours,bool>; for(constauto&[hh, pm]:{p{1h,0}, p{12h,0}, p{1h,1}, p{12h,1}}){std::cout<<std::setw(2)<< hh.count()<<(pm?"h p.m.":"h a.m.")<<" == "<<std::setw(2)<< make24(hh, pm).count()<<"h\n";}}
Output:
make12(): 0h == 12h a.m. 1h == 1h a.m.11h == 11h a.m.12h == 12h p.m.13h == 1h p.m.23h == 11h p.m. make24(): 1h a.m. == 1h12h a.m. == 0h 1h p.m. == 13h12h p.m. == 12h
