std::type_info::operator==, std::type_info::operator!=

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Utilities library

Language support Type support (basic types, RTTI) Library feature-test macros (C++20) Dynamic memory management Program utilities Coroutine support (C++20) Variadic functions is_constant_evaluated (C++20) launder (C++17) initializer_list (C++11) source_location (C++20) Three-way comparison (C++20) three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)    is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator> rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)    cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

Type support

Basic types
Fixed width integer types (C++11)
ptrdiff_t size_t max_align_t (C++11) byte (C++17)	nullptr_t (C++11) offsetof NULL
Numeric limits
numeric_limits
C numeric limits interface
Runtime type information
type_info type_index (C++11)	bad_typeid bad_cast

 

std::type_info

Member functions

type_info::~type_info

type_info::operator==type_info::operator!= (until C++20)

type_info::before

type_info::hash_code (C++11)

type_info::name

 

bool operator==( const type_info& rhs ) const;		(until C++11)
bool operator==( const type_info& rhs ) const noexcept;		(since C++11) (until C++23)
constexpr bool operator==( const type_info& rhs ) const noexcept;		(since C++23)
bool operator!=( const type_info& rhs ) const;		(until C++11)
bool operator!=( const type_info& rhs ) const noexcept;		(since C++11) (until C++20)

Checks if the objects refer to the same types.

The != operator is synthesized from operator==.

(since C++20)

Parameters

rhs

-

another type information object to compare to

Return value

true if the comparison operation holds true, false otherwise

Notes

Feature-test macro:

__cpp_lib_constexpr_typeinfo

Example

Run this code

#include <iostream>
#include <typeinfo>
#include <string>
#include <utility>
 
class person
{
  public:
    person(std::string n) : name_(std::move(n)) {}
    virtual const std::string& name() const{ return name_; }
 
  private:
    std::string name_;
};
 
class employee : public person
{
  public:
    employee(std::string n, std::string p)
      : person(std::move(n)), profession_(std::move(p)) {}
 
    const std::string& profession() const { return profession_; }
 
  private:
    std::string profession_;
};
 
void print_info(const person& p)
{
    if(typeid(person) == typeid(p))
    {
        std::cout << p.name() << " is not an employee\n";
    }
    else if(typeid(employee) == typeid(p))
    {
        std::cout << p.name() << " is an employee ";
        auto& emp = dynamic_cast<const employee&>(p);
        std::cout << "who works in " << emp.profession() << '\n';
    }
}
 
int main()
{
    print_info(employee{"Paul","Economics"});
    print_info(person{"Kate"});
 
    if constexpr (typeid(employee) != typeid(person)) // C++23
    {
        std::cout << "class `employee` != class `person`\n";
    }
}

Output:

Paul is an employee who works in Economics
Kate is not an employee
class `employee` != class `person`

See also

before

checks whether the referred type precedes referred type of another type_info object in the implementation defined order, i.e. orders the referred types (public member function)