Re: [Boost-users] [variant] how to in-place construct a variant

Stefan Strasser wrote:

I can't figure out how to in-place construct the contents of a boost::variant.

Why do you think that is supported? I see no such thing in the documentation.

so why does the following fail:

struct A : noncopyable{ A(int); A &operator=(int); }; struct B{};

int main(){ A a(5); //ok a=5; //ok variant var(5); //error var=5; //error }

Because variant requires all types it can contain to be CopyConstructible, in particular because it has no support for in-place construction or move semantics.