std::numeric_limits<T>::min_exponent

 

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基本类型
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ptrdiff_t size_t max_align_t (C++11) byte (C++17)	nullptr_t (C++11) offsetof NULL
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numeric_limits
C 数值极限接口
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type_info type_index (C++11)	bad_typeid bad_cast
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integral_constantbool_constanttrue_typefalse_type (C++11)(C++17)(C++11)(C++11)
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conjunction (C++17)
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negation (C++17)
常量求值语境
is_constant_evaluated (C++20)

受支持操作
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is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible (C++11)(C++11)(C++11)
is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible (C++11)(C++11)(C++11)
is_move_constructibleis_trivially_move_constructibleis_nothrow_move_constructible (C++11)(C++11)(C++11)
is_assignableis_trivially_assignableis_nothrow_assignable (C++11)(C++11)(C++11)
is_copy_assignableis_trivially_copy_assignableis_nothrow_copy_assignable (C++11)(C++11)(C++11)
is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable (C++11)(C++11)(C++11)
is_destructibleis_trivially_destructibleis_nothrow_destructible (C++11)(C++11)(C++11)
has_virtual_destructor (C++11)
is_swappable_withis_swappableis_nothrow_swappable_withis_nothrow_swappable (C++17)(C++17)(C++17)(C++17)
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std::numeric_limits

静态常量

numeric_limits::is_specialized

numeric_limits::is_signed

numeric_limits::is_integer

numeric_limits::is_exact

numeric_limits::has_infinity

numeric_limits::has_quiet_NaN

numeric_limits::has_signaling_NaN

numeric_limits::has_denorm

numeric_limits::has_denorm_loss

numeric_limits::round_style

numeric_limits::is_iec559

numeric_limits::is_bounded

numeric_limits::is_modulo

numeric_limits::digits

numeric_limits::digits10

numeric_limits::max_digits10 (C++11)

numeric_limits::radix

numeric_limits::min_exponent

numeric_limits::min_exponent10

numeric_limits::max_exponent

numeric_limits::max_exponent10

numeric_limits::traps

numeric_limits::tinyness_before

静态成员函数

numeric_limits::min

numeric_limits::lowest (C++11)

numeric_limits::max

numeric_limits::epsilon

numeric_limits::round_error

numeric_limits::infinity

numeric_limits::quiet_NaN

numeric_limits::signaling_NaN

numeric_limits::denorm_min

辅助类型

float_round_style

float_denorm_style

 

static const int min_exponent;		(C++11 前)
static constexpr int min_exponent;		(C++11 起)

std::numeric_limits<T>::min_exponent 的值是满足 \(\scriptsize r^{n-1}\)rn-1
是浮点类型 T 合法正规值的最低负数 n ，其中 r 是 std::numeric_limits<T>::radix 。

标准特化

T	std::numeric_limits<T>::min_exponent 的值
/* non-specialized */	​0​
bool	​0​
char	​0​
signed char	​0​
unsigned char	​0​
wchar_t	​0​
char8_t (C++20)	​0​
char16_t (C++11)	​0​
char32_t (C++11)	​0​
short	​0​
unsigned short	​0​
int	​0​
unsigned int	​0​
long	​0​
unsigned long	​0​
long long (C++11)	​0​
unsigned long long (C++11)	​0​
float	FLT_MIN_EXP
double	DBL_MIN_EXP
long double	LDBL_MIN_EXP

示例

为 float 类型演示 min_exponent、 min_exponent10、 min 及 radix 的关系：

运行此代码

#include <iostream>
int main()
{
    std::cout << "min() = " << std::numeric_limits<float>::min() << '\n'
              << "min_exponent10 = " << std::numeric_limits<float>::min_exponent10 << '\n'
              << std::hexfloat
              << "min() = " << std::numeric_limits<float>::min() << '\n'
              << "min_exponent = " << std::numeric_limits<float>::min_exponent << '\n';
}

输出：

min() = 1.17549e-38
min_exponent10 = -37
min() = 0x1p-126
min_exponent = -125

参阅

radix [静态]	给定类型的表示所用的基或整数底 (公开静态成员常量)
min_exponent10 [静态]	10 的该数次幂是合法正规浮点值的最小负数 (公开静态成员常量)
max_exponent [静态]	底的该数次幂是合法有限浮点值的最大整数加一 (公开静态成员常量)
max_exponent10 [静态]	10 的该数次幂是合法有限浮点值的最大整数 (公开静态成员常量)