chrono 文本

(C++14) <chrono> 标头定义 12 个 用户定义的文本以表示小时、分钟、秒、毫秒、微秒和纳秒。 每个用户定义的文本都具有一个整型重载和一个浮点重载。 这些文本是在 literals::chrono_literals 内联命名空间中定义的，当 std::chrono 位于范围内时，该命名空间将被自动置于范围中。

语法

inline namespace literals {
  inline namespace chrono_literals {
    // return integral days
    constexpr std::chrono::day operator"" d(unsigned long long d) noexcept;

    // return integral hours
    constexpr chrono::hours operator"" h(unsigned long long Val);

    // return floating-point hours
    constexpr chrono::duration<double, ratio<3600>> operator"" h(long double Val);

    // return integral minutes
    constexpr chrono::minutes(operator"" min)(unsigned long long Val);

    // return floating-point minutes
    constexpr chrono::duration<double, ratio<60>>(operator"" min)(long double Val);

    // return integral seconds
    constexpr chrono::seconds operator"" s(unsigned long long Val);

    // return floating-point seconds
    constexpr chrono::duration<double> operator"" s(long double Val);

    // return integral milliseconds
    constexpr chrono::milliseconds operator"" ms(unsigned long long Val);

    // return floating-point milliseconds
    constexpr chrono::duration<double, milli> operator"" ms(long double Val);

    // return integral microseconds
    constexpr chrono::microseconds operator"" us(unsigned long long Val);

    // return floating-point microseconds
    inline constexpr chrono::duration<double, micro> operator"" us(long double Val);

    // return integral nanoseconds
    inline constexpr chrono::nanoseconds operator"" ns(unsigned long long Val);

    // return floating-point nanoseconds
    constexpr chrono::duration<double, nano> operator"" ns(long double Val);

    // return integral year
    constexpr chrono::year operator""y(unsigned long long y) noexcept; // C++20
  } // inline namespace chrono_literals
} // inline namespace literals

返回值

采用 long long 参数的文本返回值或相应的类型。 采用浮点参数的文本返回 duration。

示例

下面的示例演示如何使用 chrono 文本。

constexpr auto day = 14d; // If the value > 255, then the stored value is unspecified. 
constexpr auto twoDays = 48h;
constexpr auto week = 24h* 7;
constexpr auto my_duration_unit = 108ms;
constexpr auto theYear = 2021y;