//Purpose:
//  Test code posted in:
/*
From: "Petros" <pmamales@nyc.rr.com>
Newsgroups: gmane.comp.lib.boost.user
Subject: compilation problem and a couple of boost::variant
	questions
Date: Wed, 11 Jul 2012 14:32:17 -0400
Lines: 772
 */
//
#include <boost/variant.hpp>
using boost::variant;
 
struct Zero1{ double  operator[]( const size_t i ) const { return 0L ; } };
struct One1{ double  operator[]( const size_t i ) const { return 1L ; }  };
struct Zero2{ double  operator[]( const size_t i ) const { return 0L ; } };
struct One2{ double  operator[]( const size_t i ) const { return 1L ; }  };
struct Vector1{ double  operator[]( const size_t i ) const {return double( i ) ; } };
struct Vector2{ double  operator[]( const size_t i ) const {return double( 2*i ) ; } };
struct
    subscript_operator:public boost::static_visitor<double>{
        const size_t i_;
        subscript_operator( const size_t i ):i_(i){}
 
        template<typename _v>
        double operator()( _v const & v ) const {
            return v[i_] ;
        }
};
 
 
template <typename _V, typename _Z, typename _U>
class VariantT
    :public variant< _V, _Z, _U >
{
public:
    typedef _Z zero_type ;
    typedef _U unit_type ;
 
    typedef VariantT<_V, _Z, _U>    self_type ;
    typedef variant< _V, _Z, _U >    variant_type ;
 
    template < typename _V>
    explicit VariantT( _V const & v )
        :variant_type(v)
    {}
    VariantT()
    {}
    VariantT( self_type const & v )
        :variant_type(static_cast<const variant_type&>(v))
    {}
    template < typename _V>
    VariantT & operator = ( _V const & v ) {
        *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v);
        return(*this);
    }
    VariantT & operator = ( self_type const & v ) {
        *static_cast<variant_type*>(this) = v;
        return(*this);
    }
 
    double  operator[]( const size_t i ) const {
        boost::apply_visitor( subscript_operator(i) , *this ) ;
    }
 
    bool isZero() const { return which() == 1 ; }
    bool isUnit() const { return which() == 2 ; }
 
private:
};
 
template < typename _V1, typename _V2 >
class MultVarVar{
public:
    MultVarVar( _V1 const & v1, _V2 const & v2 )
        :v1_(v1),v2_(v2)
    {}
    ~MultVarVar()
    {}
 
    typedef typename _V1::zero_type    zero_type ;
    typedef typename _V1::unit_type    unit_type ;
 
    double  operator[]( const size_t i ) const {
        return
            boost::apply_visitor ( elementwise_visitor( i ), v1, v2 ) ;
    }
 
private:
    _V1 const & v1_ ;
    _V2 const & v2_ ;
 
    struct
        elementwise_visitor
        : public boost::static_visitor< double > {
            const size_t & i_;
    public:
        elementwise_visitor( const size_t & i )
            :i_(i)
        {}
        template <typename _V1, typename _V2 >
        double operator()( _V1 const & v1, _V2 const & v2) const {
            return v1[i_] *  v2[i_] ;
        }
    };
};
 
template < typename _V1, typename _V2 >
class MultVarVarResult
    :public variant<typename MultVarVar<_V1, _V2>, typename MultVarVar<_V1,_V2>::zero_type, typename MultVarVar<_V1,_V2>::unit_type, _V1, _V2 > {
public:
    typedef variant<
        typename MultVarVar<_V1, _V2 > ,
        typename MultVarVar<_V1,_V2>::zero_type,
        typename MultVarVar<_V1,_V2>::unit_type,
        _V1,
        _V2 >                                        variant_type;
    typedef MultVarVarResult<_V1, _V2>        self_type ;
 
    typedef typename _V1::zero_type zero_type ;
    typedef typename _V1::unit_type unit_type ;
 
    template<typename _V>
    /*explicit*/ MultVarVarResult( _V const & v )
        :variant_type(v)
    {}
    MultVarVarResult( self_type const & v )
        :variant_type(static_cast<const variant_type&>(v))
    {}
    template < typename _V>
    MultVarVarResult & operator = ( _V const & v ) {
        *static_cast<variant_type*>(this) = static_cast<const variant_type&>(v);
        return(*this);
    }
    MultVarVarResult & operator = ( self_type const & v ) {
        *static_cast<variant_type*>(this) = v;
        return(*this);
    }
 
    double  operator[]( const size_t i ) const {
        boost::apply_visitor( subscript_operator(i), *this ) ;
    }
private:
};
 
template <typename _V1, typename _V2>
MultVarVarResult<_V1, _V2> operator * ( _V1 const & v1, _V2 const & v2 ) {
 
    if ( v1.isZero() || v2.isZero() )
        return
            MultVarVarResult<_V1, _V2>( typename MultVarVar<_V1,_V2>::zero_type() ) ;
    if ( v1.isUnit() )
        return
            MultVarVarResult<_V1, _V2>( v2 );
    if ( v2.isUnit() )
        return
            v1 ;
    else
        return
            MultVarVarResult<_V1, _V2>( MultVarVar<_V1, _V2>( v1, v2 ) ) ;
}
 
 
typedef VariantT< Vector1, Zero1, One1 > Variant1;
typedef VariantT< Vector2, Zero2, One2 > Variant2;
 
int main(){
    Variant1 v1;
    v1 = Zero1() ;
    Variant2 v2;
    v2 = One2()  ;
 
    auto x = v1 * v2 ;
 
    return x[0] == double(0) ;
}