std::numeric_limits::digits10

来自cppreference.com

This page has been machine-translated from the English version of the wiki using Google Translate.

The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

Click here for the English version of this page

 
C++
 
實用工具庫
類型的支持 (basic types, RTTI, type traits)
動態內存管理
錯誤處理
程序實用工具
可變參數函數
日期和時間
函數對象
initializer_list（C++11）
bitset
hash（C++11）
關係運算符
Original:
Relational operators
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
雙和元組
Original:
Pairs and tuples
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
pair
tuple（C++11）
piecewise_construct_t（C++11）
piecewise_construct（C++11）
掉期，遠期和移動
Original:
Swap, forward and move
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
swap
forward（C++11）
move（C++11）
move_if_noexcept（C++11）
declval（C++11）
 
類型的支持
基本類型
Original:
Basic types
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
基本類型
固定寬度的整數類型 （C++11）
nullptr_t（C++11）
offsetof
NULL
數值範圍內
Original:
Numeric limits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
numeric_limits
C數字限制介面
運行時類型信息
Original:
Runtime type information
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
type_info
type_index（C++11）
類型特徵
Original:
Type traits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
初級型兩類
Original:
Primary type categories
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_void（C++11）
is_array（C++11）
is_pointer（C++11）
is_enum（C++11）
is_union（C++11）
is_class（C++11）
is_function（C++11）
is_object（C++11）
is_scalar（C++11）
is_compound（C++11）
is_integral（C++11）
is_floating_point（C++11）
is_fundamental（C++11）
is_arithmetic（C++11）
is_reference（C++11）
is_lvalue_reference（C++11）
is_rvalue_reference（C++11）
is_member_pointer（C++11）
is_member_object_pointer（C++11）
is_member_function_pointer（C++11）
類型屬性
Original:
Type properties
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_const（C++11）
is_volatile（C++11）
is_pod（C++11）
is_empty（C++11）
is_polymorphic（C++11）
is_abstract（C++11）
is_trivial（C++11）
is_trivially_copyable（C++11）
is_standard_layout（C++11）
is_literal_type（C++11）
is_signed（C++11）
is_unsigned（C++11）
支持的操作
Original:
Supported operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_constructible
is_trivially_constructible
is_nothrow_constructible		（C++11）
（C++11）
（C++11）
is_default_constructible
is_trivially_default_constructible
is_nothrow_default_constructible		（C++11）
（C++11）
（C++11）
is_copy_constructible
is_trivially_copy_constructible
is_nothrow_copy_constructible		（C++11）
（C++11）
（C++11）
is_move_constructible
is_trivially_move_constructible
is_nothrow_move_constructible		（C++11）
（C++11）
（C++11）
is_assignable
is_trivially_assignable
is_nothrow_assignable		（C++11）
（C++11）
（C++11）
is_copy_assignable
is_trivially_copy_assignable
is_nothrow_copy_assignable		（C++11）
（C++11）
（C++11）
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable		（C++11）
（C++11）
（C++11）
is_destructible
is_trivially_destructible
is_nothrow_destructible		（C++11）
（C++11）
（C++11）
has_virtual_destructor（C++11）
關係和屬性查詢
Original:
Relationships and property queries
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_same（C++11）
is_base_of（C++11）
is_convertible（C++11）
alignment_of（C++11）
rank（C++11）
extent（C++11）
類型的修改
Original:
Type modifications
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
remove_cv
remove_const
remove_volatile		（C++11）
（C++11）
（C++11）
add_cv
add_const
add_volatile		（C++11）
（C++11）
（C++11）
make_signed（C++11）
make_unsigned（C++11）
remove_reference（C++11）
add_lvalue_reference
add_rvalue_reference		（C++11）
（C++11）
remove_pointer（C++11）
add_pointer（C++11）
remove_extent（C++11）
remove_all_extents（C++11）
類型轉換
Original:
Type transformations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
aligned_storage（C++11）
aligned_union（C++11）
decay（C++11）
enable_if（C++11）
conditional（C++11）
common_type（C++11）
underlying_type（C++11）
result_of（C++11）
鍵入特徵常數
Original:
Type trait constants
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
integral_constant（C++11）
 
std::numeric_limits
靜態常量
Original:
Static constants
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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
靜態成員函數
Original:
Static member functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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
助手類型
Original:
Helper types
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
float_round_style
float_denorm_style
 
static const int digits10
 （至 C++11）
static constexpr int digits10
 （C++11 起）
std::numeric_limits<T>::digits10的值的數目10為底的位數，可以不改變，即，所表示的類型T任​​何的第二個版本訂單存儲器訪問這麼多的小數位數的號碼可以轉換成一個值類型T為小數形式，沒有變化，由於四捨五入或溢出。基radix類型，它的價值是digits（digits-1浮點類型）乘以log
10(radix)和向下調整.
Original:
The value of std::numeric_limits<T>::digits10 is the number of base-10 digits that can be represented by the type T without change, that is, any number with this many decimal digits can be converted to a value of type T and back to decimal form, without change due to rounding or overflow. For base-radix types, it is the value of digits (digits-1 for floating-point types) multiplied by log
10(radix) and rounded down.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[编辑] 標準的專業

T
值的std::numeric_limits<T>::digits10
Original:
value of std::numeric_limits<T>::digits10
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
/* non-specialized */ ​0​
bool ​0​
char std::numeric_limits<char>::digits * std::log10(2)
signed char std::numeric_limits<signed char>::digits * std::log10(2)
unsigned char std::numeric_limits<unsigned char>::digits * std::log10(2)
wchar_t std::numeric_limits<wchar_t>::digits * std::log10(2)
char16_t std::numeric_limits<char16_t>::digits * std::log10(2)
char32_t std::numeric_limits<char32_t>::digits * std::log10(2)
short std::numeric_limits<short>::digits * std::log10(2)
unsigned short std::numeric_limits<signed short>::digits * std::log10(2)
int std::numeric_limits<int>::digits * std::log10(2)
unsigned int std::numeric_limits<signed int>::digits * std::log10(2)
long std::numeric_limits<long>::digits * std::log10(2)
unsigned long std::numeric_limits<unsigned long>::digits * std::log10(2)
long long std::numeric_limits<long long>::digits * std::log10(2)
unsigned long long std::numeric_limits<unsigned long long>::digits * std::log10(2)
float FLT_DIG
double DBL_DIG
long double LDBL_DIG

[编辑] 為例

一個8位二進制類型可以代表任何二位十進制數完全相同，但3位十進制數256。digits10為一個8位的值是999不能派代表出席了會議。 （8 * std::log10(2)為2.41）
Original:
An 8-bit binary type can represent any two-digit decimal number exactly, but 3-digit decimal numbers 256..999 cannot be represented. The value of digits10 for an 8-bit type is 2 (8 * std::log10(2) is 2.41)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
標準的32位IEEE 754浮點類型都有一個24位的小數部分（23位寫，一個隱含的），這可能表明，它可以代表7位數字的小數（24 * std::log10(2)是7.22）。 ，但相對舍入誤差不統一，一些浮點值與7位小數尾數也沒有生存轉化為32位的持股量和回：的最小的正面例子是8.589973e9，變成8.589974e9後的往返。這些舍入誤差可以不超過digits10，這是6.92 1位表示，(24-1)*std::log10(2)計算。向下取整結果值6.
Original:
The standard 32-bit IEEE 754 floating-point type has a 24 bit fractional part (23 bits written, one implied), which may suggest that it can represent 7 digit decimals (24 * std::log10(2) is 7.22), but relative rounding errors are non-uniform and some floating-point values with 7 decimal digits do not survive conversion to 32-bit float and back: the smallest positive example is 8.589973e9, which becomes 8.589974e9 after the roundtrip. These rounding errors cannot exceed one bit in the representation, and digits10 is calculated as (24-1)*std::log10(2), which is 6.92. Rounding down results in the value 6.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[编辑] 另請參閱

[靜態的] </ SPAN></div></div>
基數或用來表示給定類型的整數基地
Original:
the radix or integer base used by the representation of the given type
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

（公共靜態成員常量） [edit]
[靜態的] </ SPAN></div></div>
radix數量的數字，可以表示沒有變化
Original:
number of radix digits that can be represented without change
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

（公共靜態成員常量） [edit]
[靜態的] </ SPAN></div></div>
一個比最小的負電源是一個有效的標準浮點值的基數
Original:
one more than the smallest negative power of the radix that is a valid normalized floating-point value
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

（公共靜態成員常量） [edit]
[靜態的] </ SPAN></div></div>
一個比最大的整數次冪的基數是一個有效的有限浮點值
Original:
one more than the largest integer power of the radix that is a valid finite floating-point value
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

（公共靜態成員常量） [edit]

来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/types/numeric_limits/digits10&oldid=27177”