I found a strange error when I try the vec3 sample from proto, my code is like this:
struct Vec3SubscriptCtx
: proto::callable_context< Vec3SubscriptCtx const >
{
typedef int result_type;
Vec3SubscriptCtx(int i)
: i_(i)
{}
// Index array terminals with our subscript. Everything
// else will be handled by the default evaluation context.
int operator ()(proto::tag::terminal, int const (&arr)[3]) const
{
return arr[this->i_];
}
int i_;
};
struct Vec3
: proto::extends::type, Vec3>
{
explicit Vec3(int i=0, int j=0, int k=0)
{
(*this)[0] = i;
(*this)[1] = j;
(*this)[2] = k;
}
int &operator [](int i)
{
return proto::value(*this)[i];
}
int const &operator [](int i) const
{
return proto::value(*this)[i];
}
// Here we define a operator = for Vec3 terminals that
// takes a Vec3 expression.
template< typename Expr >
Vec3 &operator =(Expr const & expr)
{
typedef Vec3SubscriptCtx const CVec3SubscriptCtx;
(*this)[0] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(0));
(*this)[1] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(1));
(*this)[2] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(2));
return *this;
}
template< typename Expr >
Vec3 (Expr const & expr)
{
typedef Vec3SubscriptCtx const CVec3SubscriptCtx;
(*this)[0] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(0));
(*this)[1] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(1));
(*this)[2] = proto::eval(proto::as_expr(expr), CVec3SubscriptCtx(2));
}
void print() const
{
std::cout << '{' << (*this)[0]
<< ", " << (*this)[1]
<< ", " << (*this)[2]
<< '}' << std::endl;
}
};
int main(int argc, const char* argv[])
{
Vec3 a(1, 2, 3);
Vec3 b(3, 2, 1);
Vec3 c;
c = b;
c.print();
return 0;
}
I expected that when c is printed it will display 3, 2, 1 ( the value of b ) but instead it print 0,0,0 like b is never assigned to c. I try this using vs 2010 with boost 1.44 in windows 7 64.
