Re: Are there mixed type containers?

On 11 mar, 01:05, DeMarcus <nob...@tellus.orb.sunsite.dk> wrote:


Of course it won't work.
As said to use something not unlike boost.any, not boost.any itself.

A quick implementation I'm writing just for this message (so no well
tested, may contain bugs):

#include <boost/utility.hpp>
#include <algorithm>
#include <ostream>

struct streamable_impl_base : boost::noncopyable
{
     virtual streamable_impl_base* clone() = 0;
     virtual std::ostream& stream(std::ostream& os) = 0;

     virtual ~streamable_impl_base()
     {
     }
};

template<typename T>
struct streamable_impl : streamable_impl_base
{
     streamable_impl(const T& t_) : t(t_)
     {
     }

     streamable_impl_base* clone()
     {
         return new streamable_impl<T>(t);
     }

     std::ostream& stream(std::ostream& os)
     {
         return os << t;
     }

private:
     T t;
};

struct streamable
{
     template<typename T>
     streamable(const T& t) : p(new streamable_impl<T>(t))
     {
     }

     streamable(const streamable& s) : p(s.p->clone())
     {
     }

     streamable& operator=(streamable s)
     {
         swap(s);
         return *this;
     }

     void swap(streamable& s)
     {
         std::swap(p, s.p);
     }

     ~streamable()
     {
         delete p;
     }

     friend std::ostream& operator<<(std::ostream& os, const
streamable& s)
     {
         return s.p->stream(os);
     }

private:
     streamable_impl_base* p;
};

Now use streamable instead of any:

std::vector<streamable> args;
args.push_back( (const char*)"Hello" ); // arrays are not
CopyConstructible
args.push_back( 4711 );

for( std::vector<streamable>::iterator i = args.begin(); i !=
      args.end(); ++i )
     std::cout << (*i) << std::endl;

I even tested it and verified it worked as expected.

Note, however, that I still do not see why you would be needing this
to do a lazy cout.

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