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is_convertible

template <class From, class To>
struct is_convertible : public true_type-or-false_type {};

Inherits: If an imaginary rvalue of type From is convertible to type To then inherits from true_type, otherwise inherits from false_type.

Type From must not be an incomplete type.

Type To must not be an incomplete, or function type.

No types are considered to be convertible to array types or abstract-class types.

This template can not detect whether a converting-constructor is public or not: if type To has a private converting constructor from type From then instantiating is_convertible<From, To> will produce a compiler error. For this reason is_convertible can not be used to determine whether a type has a public copy-constructor or not.

This template will also produce compiler errors if the conversion is ambiguous, for example:

struct A {};
struct B : A {};
struct C : A {};
struct D : B, C {};
// This produces a compiler error, the conversion is ambiguous:
bool const y = boost::is_convertible<D*,A*>::value;

C++ Standard Reference: 4 and 8.5.

Compiler Compatibility: This template is currently broken with Borland C++ Builder 5 (and earlier), for constructor-based conversions, and for the Metrowerks 7 (and earlier) compiler in all cases. If the compiler does not support is_abstract, then the template parameter To must not be an abstract type.

Header: #include <boost/type_traits/is_convertible.hpp> or #include <boost/type_traits.hpp>

Examples:

is_convertible<int, double> inherits from true_type.

is_convertible<const int, double>::type is the type true_type.

is_convertible<int* const, int*>::value is an integral constant expression that evaluates to true.

is_convertible<int const*, int*>::value is an integral constant expression that evaluates to false: the conversion would require a const_cast.

is_convertible<int const&, long>::value is an integral constant expression that evaluates to true.

is_convertible<int, int>::value is an integral constant expression that evaluates to true.

is_convertible<T, T>::value_type is the type bool.


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