# <typeinfo>

<head><title>&lt;typeinfo&gt;</title></head>

# `<typeinfo>`

* * *

Include the standard header **`<typeinfo>`**
to define several types associated with the type-identification operator
**`typeid`**,
which yields information about both static and dynamic types.

    namespace std {
    class type_info;
    class bad_cast;
    class bad_typeid;
    }  // namespace stdCopy to clipboard

## `bad_cast`

    class bad_cast : public exception {
        };Copy to clipboard

The class describes an exception thrown to indicate that a
**dynamic cast** expression,
of the form:

    dynamic_cast<type>(expression)Copy to clipboard

generated a null pointer to initialize a reference.
The value returned by
`what()`
is an implementation-defined
[C string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#C%20string).
None of the member functions throw any exceptions.

## `bad_typeid`

    class bad_typeid : public exception {
        };Copy to clipboard

The class describes an exception thrown to indicate that a
[`typeid`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_typeinfo.html#typeid) operator encountered a
null pointer. The value returned by
`what()`
is an implementation-defined
[C string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#C%20string).
None of the member functions throw any exceptions.

## `type_info`

    class type_info {
    public:
        virtual ~type_info();
        bool operator==(const type_info& right) const;
        bool operator!=(const type_info& right) const;
        bool before(const type_info& right) const;
        const char *name() const;
    private:
        type_info(const type_info& right);
        type_info& operator=(const type_info& right);
        };Copy to clipboard

The class describes type information generated
within the program by the implementation. Objects of this class effectively
store a pointer to a
**name** for the type,
and an encoded value suitable for comparing two types for equality or
**collating order**.
The names, encoded values, and collating order for types
are all unspecified and may differ between program executions.

An expression of the form `typeid Ty` is the *only* way to
construct a (temporary) `typeinfo` object. The class has only
a private copy constructor. Since the assignment operator is also
private, you cannot copy or assign objects of class `typeinfo`
either.

### `type_info::operator!=`

    bool operator!=(const type_info& right) const;Copy to clipboard

The function returns `!(*this
== right)`.

### `type_info::operator==`

    bool operator==(const type_info& right) const;Copy to clipboard

The function returns a nonzero value if `*this`
and `right` represent the same type.

### `type_info::before`

    bool before(const type_info& right) const;Copy to clipboard

The function returns a nonzero value if `*this`
precedes `right` in the
[collating order](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_typeinfo.html#collating%20order%20for%20types) for types.

### `type_info::name`

    const char *name() const;Copy to clipboard

The function returns a
[C string](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_over.html#C%20string) which specifies the
[name](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_typeinfo.html#names%20for%20types) of the type.

* * *

See also the
**[Table of Contents](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_index.html#Table%20of%20Contents)** and the
**[Index](https://docs.qualcomm.com/doc/80-N3040-23/topic/_cpp_index.html)**.

*[Copyright](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_crit_pjp.html) © 1992-2006by P.J. Plauger. All rights reserved.*

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Last Published: Oct 06, 2026

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