error_category Class

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The latest version of this topic can be found at error_category Class.

Represents the abstract, common base for objects that describes a category of error codes.

Syntax

class error_category;

Remarks

Two predefined objects implement error_category: generic_category and system_category.

TypeDefs

value_type A type that represents the stored error code value.

Member Functions

default_error_condition Stores the error code value for an error condition object.
equivalent Returns a value that specifies whether error objects are equivalent.
message Returns the name of the specified error code.
name Returns the name of the category.

Operators

operator== Tests for equality between error_category objects.
operator!= Tests for inequality between error_category objects.
operator< Tests if the error_category object is less than the error_category object passed in for comparison.

Requirements

Header: <system_error>

Namespace: std

error_category::default_error_condition

Stores the error code value for an error condition object.

virtual error_condition default_error_condition(int _Errval) const;

Parameters

Parameter Description
_Errval The error code value to store in the error_condition.

Return Value

Returns error_condition(_Errval, *this).

Remarks

error_category::equivalent

Returns a value that specifies whether error objects are equivalent.

virtual bool equivalent(value_type _Errval,
    const error_condition& _Cond) const;

virtual bool equivalent(const error_code& _Code,
    value_type _Errval) const;

Parameters

Parameter Description
_Errval The error code value to compare.
_Cond The error_condition object to compare.
_Code The error_code object to compare.

Return Value

true if the category and value are equal; otherwise, false.

Remarks

The first member function returns *this == _Cond.category() && _Cond.value() == _Errval.

The second member function returns *this == _Code.category() && _Code.value() == _Errval.

error_category::message

Returns the name of the specified error code.

virtual string message(error_code::value_type val) const = 0;

Parameters

Parameter Description
val The error code value to describe.

Return Value

Returns a descriptive name of the error code val for the category.

Remarks

error_category::name

Returns the name of the category.

virtual const char *name() const = 0;

Return Value

Returns the name of the category as a null-terminated byte string.

Remarks

error_category::operator==

Tests for equality between error_category objects.

bool operator==(const error_category& right) const;

Parameters

Parameter Description
right The object to be tested for equality.

Return Value

true if the objects are equal; false if the objects are not equal.

Remarks

This member operator returns this == &right.

error_category::operator!=

Tests for inequality between error_category objects.

bool operator!=(const error_category& right) const;

Parameters

Parameter Description
right The object to be tested for inequality.

Return Value

true if the error_category object is not equal to the error_category object passed in right; otherwise false.

Remarks

The member operator returns (!*this == right).

error_category::operator<

Tests if the error_category object is less than the error_category object passed in for comparison.

bool operator<(const error_category& right) const;

Parameters

Parameter Description
right The error_category object to be compared.

Return Value

true if the error_category object is less than the error_category object passed in for comparison; Otherwise, false.

Remarks

The member operator returns this < &right.

error_category::value_type

A type that represents the stored error code value.

typedef int value_type;

Remarks

This type definition is a synonym for int.

See Also

<system_error>