From: Joel de Guzman (djowel_at_[hidden])
Date: 2003-10-04 05:12:51
Sounds like a variant to me. What am I missing?
--
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net
E. Gladyshev <egladysh_at_[hidden]> wrote:
> Just wondering does boost have something similar to C unions
> so that you could create heterogenious containers?
>
> Something like the following working pseudo-code
>
> template < typename Types >
> struct union2
> {
> typedef typename boost::mpl::at_c<Types, 0 >::type type1;
> typedef typename boost::mpl::at_c<Types, 1 >::type type2;
>
> union2() : obj_(0)
> {
> }
> union2( const union2<Types>& l ) : obj_(0)
> {
> create( l.t_ );
> copy( l.obj_ );
> }
> virtual ~union2()
> {
> free();
> }
>
> void create( size_t t )
> {
> free();
> t_ = t;
> switch( t_ )
> {
> case 0:
> obj_ = new type1;
> break;
>
> case 1:
> obj_ = new type2;
> break;
>
> default:
> throw;
> }
> }
>
> private:
> size_t t_;
> void *obj_;
> void free()
> {
> if( !obj_ ) return;
> switch( t_ )
> {
> case 0:
> delete static_cast<type1*>(obj_);
> break;
>
> case 1:
> delete static_cast<type2*>(obj_);
> break;
>
> default:
> throw;
> }
> obj_ = 0;
> }
>
> void copy( void* obj )
> {
> switch( t_ )
> {
> case 0:
> *static_cast<type1*>(obj_) = *static_cast<type1*>(obj);
> break;
>
> case 1:
> *static_cast<type2*>(obj_) = *static_cast<type2*>(obj);
> break;
>
> default:
> throw;
> }
> }
> };
>
> main()
> {
> typedef notus::union2< boost::mpl::vector2<char, short> > my_union;
>
> std::vector< my_union > gv;
>
> my_union u(0);
> my_union u1(1);
> gv.push_back( u );
> gv.push_back( u1 );
> }
>
>
> Eugene
>
>
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