boost::bad_get The exception thrown in the event of a failed application of boost::polymorphic_get on the given operand value. const char * U * variant<T1, T2, ..., TN> * const U * const variant<T1, T2, ..., TN> * U & variant<T1, T2, ..., TN> & const U & const variant<T1, T2, ..., TN> & Retrieves a value of a specified type from a given variant. The polymorphic_get function allows run-time checked, type-safe retrieval of the content of the given variant. The function succeeds only if the content is of the specified type U or of type derived from type U, with failure indicated as described below. Warning: After either operand or its content is destroyed (e.g., when the given variant is assigned a value of different type), the returned reference is invalidated. Thus, significant care and caution must be extended when handling the returned reference. As part of its guarantee of type-safety, polymorphic_get enforces const-correctness. Thus, the specified type U must be const-qualified whenever operand or its content is likewise const-qualified. The converse, however, is not required: that is, the specified type U may be const-qualified even when operand and its content are not. If passed a pointer, polymorphic_get returns a pointer to the value content if it is of the specified type U or of type derived from type U; otherwise, a null pointer is returned. If passed a reference, polymorphic_get returns a reference to the value content if it is of the specified type U or of type derived from type U; otherwise, an exception is thrown (see below). Overloads taking a variant pointer will not throw; the overloads taking a variant reference throw bad_polymorphic_get if the content is not of the specified type Uor of type derived from type U. While visitation via apply_visitor is generally preferred due to its greater safety, polymorphic_get may may be more convenient in some cases due to its straightforward usage.