Swap the alternative having index (template parameter) t_INDEX in *d_variant_p with the specified value (i.e. the alternative that is being visited). The behavior is undefined unless t_INDEX is the index of the active alternative of *d_variant_p (or, in C++03, the index of an alternative that has the same type as the active alternative).
Declared in <bslstl_variant.h>
template<
size_t t_INDEX,
class t_TYPE>
void
operator()(
bsl::in_place_index_t<t_INDEX>,
t_TYPE& value) const;