std::is_convertible

 

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type_info type_index (C++11)	bad_typeid bad_cast

 

Defined in header <type_traits>
template< class From, class To > struct is_convertible;		(since C++11)

If the return statement in the imaginary function definition To test() { return std::declval<From>(); } is well-formed, (that is, if std::declval<From>() can be converted to To using implicit conversion), provides the member constant value equal to true. Otherwise value is false. For the purposes of this check, the use of std::declval is in the return statement is not considered an odr-use.

If From or To is not a complete type, (possibly cv-qualified) void, or an array of unknown bound, the behavior is undefined.

If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.

Helper variable template

template< class From, class To > constexpr bool is_convertible_v = is_convertible<From, To>::value;		(since C++17)

Inherited from std::integral_constant

Member constants

value [static]

true if From is convertible to To , false otherwise (public static member constant)

Member functions

operator bool	converts the object to bool, returns value (public member function)
operator() (C++14)	returns value (public member function)

Member types

Type	Definition
value_type	bool
type	std::integral_constant<bool, value>

Notes

Gives well-defined results for reference types, void types, array types, and function types.

Example

Run this code

#include <iostream>
#include <type_traits>
 
int main() 
{
    class A {};
    class B : public A {};
    class C {};
 
    bool b2a = std::is_convertible<B*, A*>::value;
    bool a2b = std::is_convertible<A*, B*>::value;
    bool b2c = std::is_convertible<B*, C*>::value;
 
    std::cout << std::boolalpha;
    std::cout << b2a << '\n';
    std::cout << a2b << '\n';
    std::cout << b2c << '\n';
}

Output:

true
false
false

See also

std::experimental::is_convertible_v (library fundamentals TS)

variable template alias of std::is_convertible::value (variable template)