//SGObject.h
public:
    template<class T>
    bool equals(const Some<T> & other, float64_t accuracy=0.0, bool tolerant=false)
    {
        equals_impl(some_dynamic_cast<CSGObject>(other), accuracy, tolerant);
    };

protected:
    virtual bool equals_impl(const Some<CSGObject> & other, float64_t accuracy=0.0, bool tolerant=false)
    {
        /** actual equals code **/
    }

//some.h
template <typename U, typename T>
    Some<U> some_dynamic_cast(const Some<T> & other)
    {
        U * tmp = dynamic_cast<U*>(other.get());
        if (tmp==NULL)
            return Some<U>::from_raw(nullptr);
        return Some<U>::from_raw(tmp);
    }