std::underflow_error
Defined in header <stdexcept>
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class underflow_error; |
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Defines a type of object to be thrown as exception. It may be used to report arithmetic underflow errors (that is, situations where the result of a computation is a subnormal floating-point value).
The standard library components do not throw this exception (mathematical functions report underflow errors as specified in math_errhandling). Third-party libraries, however, use this. For example, boost.math throws std::underflow_error if boost::math::policies::throw_on_error
Inheritance diagram
Member functions
(constructor) |
constructs a new underflow_error object with the given message (public member function) |
operator= |
replaces the underflow_error object (public member function) |
std::underflow_error::underflow_error
|
underflow_error(
const
std::string
& what_arg )
;
|
(1) | |
|
underflow_error( const char* what_arg );
|
(2) | |
underflow_error( const underflow_error& other ); |
(3) | (noexcept since C++11) |
std::underflow_error then
std::strcmp
(what(
), other.what
(
)
)
==
0
Parameters
| what_arg | - | explanatory string |
| other | - | another exception object to copy |
Exceptions
Notes
Because copying std::underflow_error is not permitted to throw exceptions, this message is typically stored internally as a separately-allocated reference-counted string. This is also why there is no constructor taking std::string&&
Before the resolution of LWG issue 254, the non-copy constructor can only accept std::string. It makes dynamic allocation mandatory in order to construct a std::string
After the resolution of LWG issue 471
what()
std::underflow_error::operator=
|
underflow_error& operator=
(
const underflow_error& other )
;
|
(noexcept since C++11) | |
Assigns the contents with those of other. If *this and other both have dynamic type std::underflow_error then
std::strcmp
(what(
), other.what
(
)
)
==
0
Parameters
| other | - | another exception object to assign with |
Return value
*this
Notes
After the resolution of LWG issue 471
what()
Inherited from std::runtime_error
Inherited from std::exception
Member functions
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[virtual]
|
destroys the exception object (virtual public member function of std::exception) |
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[virtual]
|
returns an explanatory string (virtual public member function of std::exception) |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 254 | C++98 | the constructor accepting const char* was missing | added |
| LWG 471 | C++98 | the explanatory strings of std::underflow_error'scopies were implementation-defined |
they are the same as that of the original std::underflow_error object
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