Re: Is run-time switching on type traits bad?

Hi,

Is run-time switching on type traits as bad as switching on class type?
(Sutter & Alexandrescu, C++ Coding Standards, Item 90 - Avoid type
switching)

I.e. should type traits be for compile time only?

A run-time example:

class VisitableInterface
{
public:
    virtual ~VisitableInterface() {}

    virtual void accept( Visitor& v ) const = 0;
    virtual bool isPOD() const = 0;
};

template<typename T>
class SomeVisitable : public VisitableInterface
{
public:
    SomeVisitable( const T& element ) : element_(element) {}

    virtual void accept( Visitor& v ) const
    {
       ...
    }

    virtual bool isPOD() const
    {
       return std::is_pod<T>::value;
    }

private:
    const T element_;
};

int main()
{
    std::vector<VisitableInferface*> vec;
    PodVisitor podVisitor;
    ClassVisitor classVisitor;

    for( auto i = vec.begin(); i != vec.end(); ++i )
    {
       if( (*i)->isPOD() )
          (*i)->accept( podVisitor );
       else
          (*i)->accept( classVisitor );
    }
}