<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 std

bad_cast

class bad_cast
    : public exception
    {  // reports an exception
    };

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

dynamic_cast<type>(expression)

generated a null pointer to initialize a reference. The value returned by what() is an implementation-defined C string. None of the member functions throw any exceptions.

bad_typeid

class bad_typeid
    : public exception
    {  // reports a bad typeid
    };

The class describes an exception thrown to indicate that a typeid operator encountered a null pointer. The value returned by what() is an implementation-defined C string. None of the member functions throw any exceptions.

type_info

class type_info {
public:
    virtual ~type_info();
    type_info(const type_info& right) = delete; [added with C++11]
    type_info& operator=(const type_info& right) = delete; [added with C++11]

    size_t hash_code() const; [added with C++11]
    bool before(const type_info& right) const noexcept;
    const char *name() const noexcept;

    bool operator==(const type_info& right) const noexcept;
    bool operator!=(const type_info& right) const noexcept;
    };

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::before

bool before(const type_info& right) const noexcept;

The member function returns a nonzero value if *this precedes right in the collating order for types.

type_info::hash_code

size_t hash_code() const; [added with C++11]

The member function defines a hash function, suitable for mapping values of type typeinfo to a distribution of index values.

type_info::name

const char *name() const noexcept;

The member function returns a C string which specifies the name of the type.

type_info::operator!=

bool operator!=(const type_info& right) const noexcept;

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

type_info::operator==

bool operator==(const type_info& right) const noexcept;

The member operator returns a nonzero value if *this and right represent the same type.

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Copyright © 1992-2013 by P.J. Plauger. All rights reserved.