[boost] Re: problems with binary variant visitors in 1.31

From: E. Gladyshev (egladysh_at_[hidden])
Date: 2004-02-06 05:56:15

Never mind. Sorry I didn't notice 'const' in data().
Everything is pefect now.

Eugene

--- "E. Gladyshev" <egladysh_at_[hidden]> wrote:
> Great job with the 1.31 release!
> 
> Just wondering if anybody else observerved this kind of problems before.
> When compiling the code below with MSVC 7.1, I am getting this error:
> test.cpp(123) : error C2039: 'set' : is not a member of 'my_type::test1'.  
> GCC 3.2.3 gives a compilation error as well.
> 
> template< typename T >
> struct binary_variant_visitor : public ::boost::static_visitor<>
> {
>     T& obj_;
>     
>     binary_variant_visitor( T& obj ) : obj_(obj) {}
>     
>     template< typename VT1, typename VT2 >
>     void operator()( VT1& v1, VT2& v2 )
>     {
>         obj_.visit( v1, v2 );
>     }
> };
> 
> struct my_type
> {
>     struct test1
>     {
>         test1();
>         ~test1();
>     };
>     struct test2
>     {
>         ~test2();
>         template< typename T >
>         void set( T& );
>     };
>     
>     typedef ::boost::variant<test1,test2> var;
>     
>     var d_;
>     
>     template< typename U >
>     void visit( test1& t, U& u )   //test1 doesn't have set()
>     {
>     }
>     
>     template< typename T, typename U >      
>     void visit( T& t, U& u )
>     {
>         t.set(u);
>     }
>     
>     const var& data() const { return d_; }
> };
> 
> main()
> {
>     my_type t1, t2;
>     
>     binary_variant_visitor<my_type> v(t1);
>     ::boost::apply_visitor(v, t1.data(), t2.data() );
> }
> 
> If I change the last line to
>   ::boost::apply_visitor(v, t1.d_, t2.d_ );
> 
> it works fine on both compilers.
> I guess it has something to do with how 
> apply_visitor derives the parameter types.
> 
> Eugene
> 
> 
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