Difference between revisions of "cpp/error/error code/is error code enum"
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< cpp | error | error code
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{{cpp/title|is_error_code_enum}} | {{cpp/title|is_error_code_enum}} | ||
{{cpp/error/error_code/navbar}} | {{cpp/error/error_code/navbar}} | ||
| − | {{ | + | {{ddcl|header=system_error|since=c++11| |
| − | + | ||
| − | + | ||
template< class T > | template< class T > | ||
struct is_error_code_enum; | struct is_error_code_enum; | ||
}} | }} | ||
| − | |||
| − | If {{tt|T}} is an error code enumeration, this template provides the member constant {{c|value}} equal {{c|true}}. | + | If {{tt|T}} is an error code enumeration (such as {{lc|std::io_errc}} and {{lc|std::future_errc}}), this template provides the member constant {{c|value}} equal {{c|true}}. For any other type, {{c|value}} is {{c|false}}. |
| − | This template may be specialized for a | + | This template may be specialized for a {{lsd|cpp/language/type#Program-defined type}} to indicate that the type is eligible for {{lc|std::error_code}} implicit conversion. |
| − | + | ===Helper variable template=== | |
| − | + | {{ddcl|since=c++17|1= | |
| − | + | ||
| − | + | ||
| − | === Helper variable template === | + | |
| − | {{ddcl | since=c++17 | 1= | + | |
template< class T > | template< class T > | ||
| − | + | constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value; | |
}} | }} | ||
| − | {{cpp/types/integral_constant/inherit | {{tt|T}} is an error code enum}} | + | {{cpp/types/integral_constant/inherit|{{tt|T}} is an error code enum}} |
| + | |||
| + | {{example | ||
| + | |code= | ||
| + | #include <ios> | ||
| + | #include <system_error> | ||
| + | |||
| + | static_assert(std::is_error_code_enum_v<decltype(std::io_errc::stream)>); | ||
| + | static_assert(!std::is_error_code_enum_v<std::error_category>); | ||
| + | |||
| + | int main() {} | ||
| + | }} | ||
===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/error/error_condition/dsc is_error_condition_enum}} | + | {{dsc inc|cpp/error/error_condition/dsc is_error_condition_enum}} |
| − | + | ||
{{dsc end}} | {{dsc end}} | ||
| − | {{langlinks|zh}} | + | {{langlinks|es|ja|ru|zh}} |
Latest revision as of 08:51, 24 September 2024
| Defined in header <system_error>
|
||
| template< class T > struct is_error_code_enum; |
(since C++11) | |
If T is an error code enumeration (such as std::io_errc and std::future_errc), this template provides the member constant value equal true. For any other type, value is false.
This template may be specialized for a program-defined type to indicate that the type is eligible for std::error_code implicit conversion.
Contents |
[edit] Helper variable template
| template< class T > constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value; |
(since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] |
true if T is an error code enum, false otherwise (public static member constant) |
Member functions
| operator bool |
converts the object to bool, returns value (public member function) |
| operator() (C++14) |
returns value (public member function) |
Member types
| Type | Definition |
value_type
|
bool |
type
|
std::integral_constant<bool, value> |
Run this code
#include <ios> #include <system_error> static_assert(std::is_error_code_enum_v<decltype(std::io_errc::stream)>); static_assert(!std::is_error_code_enum_v<std::error_category>); int main() {}
[edit] See also
| (C++11) |
identifies an enumeration as an std::error_condition (class template) |
