C++ 库 - <限制>

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介绍

它是一种数字限制类型，提供有关库编译的特定平台中算术类型（整型或浮点型）属性的信息。

宣言

以下是 std::numeric_limits 的声明。

template <class T> numeric_limits; 

C++11

template <class T> numeric_limits; 

参数

T - 它是一种类。

例子

在下面的 std::numeric_limits 示例中。

#include <limits>
#include <iostream>

int main() {
   std::cout << "type\tlowest type\thighest type\n";
   std::cout << "int\t"
      << std::numeric_limits<int>::lowest() << '\t'
      << std::numeric_limits<int>::max() << '\n';
   std::cout << "float\t"
      << std::numeric_limits<float>::lowest() << '\t'
      << std::numeric_limits<float>::max() << '\n';
   std::cout << "double\t"
      << std::numeric_limits<double>::lowest() << '\t'
      << std::numeric_limits<double>::max() << '\n';
}

示例输出应该是这样的 -

type	lowest type	highest type
int	-2147483648	2147483647
float	-3.40282e+38	3.40282e+38
double	-1.79769e+308	1.79769e+308

模板实例化

C++98 的基本算术类型应该是这样的 -

C++11 的基本算术类型应该是这样的 -

会员

对于上述所有非基本算术类型的类型，使用默认模板定义 -

C++98

template <class T> class numeric_limits {
   public:
      static const bool is_specialized = false;
      static T min() throw();
      static T max() throw();
      static const int digits = 0;
      static const int digits10 = 0;
      static const bool is_signed = false;
      static const bool is_integer = false;
      static const bool is_exact = false;
      static const int radix = 0;
      static T epsilon() throw();
      static T round_error() throw();

      static const int min_exponent = 0;
      static const int min_exponent10 = 0;
      static const int max_exponent = 0;
      static const int max_exponent10 = 0;

      static const bool has_infinity = false;
      static const bool has_quiet_NaN = false;
      static const bool has_signaling_NaN = false;
      static const float_denorm_style has_denorm = denorm_absent;
      static const bool has_denorm_loss = false;
      static T infinity() throw();
      static T quiet_NaN() throw();
      static T signaling_NaN() throw();
      static T denorm_min() throw();

      static const bool is_iec559 = false;
      static const bool is_bounded = false;
      static const bool is_modulo = false;

      static const bool traps = false;
      static const bool tinyness_before = false;
      static const float_round_style round_style = round_toward_zero;
};

C++11

template <class T> class numeric_limits {
   public:
      static constexpr bool is_specialized = false;
      static constexpr T min() noexcept { return T(); }
      static constexpr T max() noexcept { return T(); }
      static constexpr T lowest() noexcept { return T(); }
      static constexpr int digits = 0;
      static constexpr int digits10 = 0;
      static constexpr bool is_signed = false;
      static constexpr bool is_integer = false;
      static constexpr bool is_exact = false;
      static constexpr int radix = 0;
      static constexpr T epsilon() noexcept { return T(); }
      static constexpr T round_error() noexcept { return T(); }

      static constexpr int min_exponent = 0;
      static constexpr int min_exponent10 = 0;
      static constexpr int max_exponent = 0;
      static constexpr int max_exponent10 = 0;

      static constexpr bool has_infinity = false;
      static constexpr bool has_quiet_NaN = false;
      static constexpr bool has_signaling_NaN = false;
      static constexpr float_denorm_style has_denorm = denorm_absent;
      static constexpr bool has_denorm_loss = false;
      static constexpr T infinity() noexcept { return T(); }
      static constexpr T quiet_NaN() noexcept { return T(); }
      static constexpr T signaling_NaN() noexcept { return T(); }
      static constexpr T denorm_min() noexcept { return T(); }

      static constexpr bool is_iec559 = false;
      static constexpr bool is_bounded = false;
      static constexpr bool is_modulo = false;

      static constexpr bool traps = false;
      static constexpr bool tinyness_before = false;
};