c++ - 在Visual Studio 2019中使用numeric_limits错误的C++长双倍最小值/最大值

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long double vs double

(3个答案)


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将Visual Studio Community 2019 v16.4.2与64位Win10附带的最新内容一起使用。

在测试各种数据类型限制时遇到了一个奇怪的错误，numeric_limits不能区分double和long double min / max值。使用带有默认GNU Mac工具链的NetBeans显示更合理的结果。

    // Type limits: float
    std::cout 
        << "MIN float        " << numeric_limits<float>::min() << "\n"
        << "MAX float        " << numeric_limits<float>::max() << "\n"
        << "MIN double       " << numeric_limits<double>::min() << "\n"
        << "MAX double       " << numeric_limits<double>::max() << "\n"
        << "MIN long double  " << numeric_limits<long double>::min() << "\n"
        << "MAX long double  " << numeric_limits<long double>::max() << "\n";

控制台输出

MIN float        1.17549e-38
MAX float        3.40282e+38
MIN double       2.22507e-308
MAX double       1.79769e+308
MIN long double  2.22507e-308    // NetBeans on Mac 3.3621e-4932
MAX long double  1.79769e+308    // NetBeans on Mac 1.18973e+4932

最佳答案

C++标准仅要求long double至少具有double的精度，因此程序的输出没有任何问题。

从标准中引用(第3.9.1节，点亮8):

There are three floating point types: float,double, and long double.The type double provides at least as much precision as float, and the type long double provides at least as much precision as double.The set of values of the type float is a subset of the set of values of the type double; the set of values of the type double is a subset of the set of values of the type long double. The value representation of floating-point types is implementation-defined. Integral and floating types are collectively called arithmetic types. Specializations of the standard template std::numeric_limits (18.3) shall specify the maximum and minimum values of each arithmetic type for an implementation.

关于c++ - 在Visual Studio 2019中使用numeric_limits错误的C++长双倍最小值/最大值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/59612007/

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Answer 1

C++标准仅要求long double至少具有double的精度，因此程序的输出没有任何问题。

从标准中引用(第3.9.1节，点亮8):

There are three floating point types: float,double, and long double.The type double provides at least as much precision as float, and the type long double provides at least as much precision as double.The set of values of the type float is a subset of the set of values of the type double; the set of values of the type double is a subset of the set of values of the type long double. The value representation of floating-point types is implementation-defined. Integral and floating types are collectively called arithmetic types. Specializations of the standard template std::numeric_limits (18.3) shall specify the maximum and minimum values of each arithmetic type for an implementation.