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std::numeric_limits::digits10

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C++
 
Bibliothèque d'utilitaires
 
Soutien aux types fondamentaux
Les types de base
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Basic types
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Types fondamentaux
Fixe les types entiers largeur (C++11)
Limites numériques
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Numeric limits
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numeric_limits
C numérique limite interface
Informations sur le type d'exécution
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Runtime type information
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Caractères de type
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Type traits
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Catégories de type primaire
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Primary type categories
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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)
Les propriétés du type
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Type properties
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is_const (C++11)
is_volatile (C++11)
is_pod (C++11)
is_empty (C++11)
is_polymorphic (C++11)
is_abstract (C++11)
Opérations prises en charge
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Supported operations
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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)
Les relations et les requêtes de propriété
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Relationships and property queries
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is_same (C++11)
is_base_of (C++11)
is_convertible (C++11)
alignment_of (C++11)
rank (C++11)
extent (C++11)
Modifications de type
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Type modifications
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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)
Transformations de type
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Type transformations
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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)
Tapez constantes traits
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Type trait constants
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integral_constant (C++11)
 
std::numeric_limits
Constantes statiques
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Static constants
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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
Fonctions membres statiques
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Static member functions
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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
Types d'aide
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Helper types
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float_round_style
float_denorm_style
 
static const int digits10
 (avant C++11)
static constexpr int digits10
 (depuis C++11)
La valeur de std::numeric_limits<T>::digits10 est le nombre de base de-10 chiffres pouvant être représenté par la T type sans changement, c'est-à-tout nombre de chiffres à ce décimales peut être converti en une valeur de T type et revenir à la forme décimale, sans changement en raison de l'arrondissement ou de débordement. Pour de bases radix types, c'est la valeur de digits (digits-1 de types à virgule flottante) multiplié par log
10(radix) et arrondi vers le bas .
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.
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[modifier] Spécialisations standard

T
valeur de std::numeric_limits<T>::digits10
Original:
value of std::numeric_limits<T>::digits10
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/* 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

[modifier] Exemple

Un type binaire 8-bit peut représenter n'importe quel nombre décimal à deux chiffres exactement, mais à 3 chiffres décimaux 256 .. 999 ne peut pas être représenté. La valeur de digits10 pour un type 8-bit est 2 (8 * std::log10(2) vaut 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)
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La norme 32 bits IEEE 754 type en virgule flottante a une partie fractionnaire 24 bits (23 bits par écrit, un sous-entendu), ce qui pourrait suggérer qu'il puisse représenter le 7 décimales (chiffres 24 * std::log10(2) est 7.22) , mais des erreurs d'arrondi relatives ne sont pas uniformes et certaines valeurs à virgule flottante avec 7 chiffres après la virgule ne survivent pas à la conversion en 32-bit float et à l'arrière: le plus petit exemple positif est 8.589973e9, qui devient 8.589974e9 après l'aller-retour Ces erreurs d'arrondi ne peut pas dépasser. un bit dans la représentation, et digits10 est calculé comme (24-1)*std::log10(2), qui est 6.92. arrondi à la baisse des résultats de la valeur 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.
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[modifier] Voir aussi

[
statique
Original:
static
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]
la base ou la base utilisée par nombre entier de la représentation du type donné
Original:
the radix or integer base used by the representation of the given type
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(constante membre statique publique) [edit]
[
statique
Original:
static
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]
nombre de chiffres radix qui peuvent être représentées sans changement
Original:
number of radix digits that can be represented without change
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(constante membre statique publique) [edit]
[
statique
Original:
static
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]
un de plus que la plus petite puissance négative de la racine qui est valide normalisé valeur à virgule flottante
Original:
one more than the smallest negative power of the radix that is a valid normalized floating-point value
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(constante membre statique publique) [edit]
[
statique
Original:
static
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]
un de plus que la plus grande puissance entière de la racine qui est valide finie valeur à virgule flottante
Original:
one more than the largest integer power of the radix that is a valid finite floating-point value
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(constante membre statique publique) [edit]
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