U++ forum: Welcome to the forum

Re: the container type UPP::Link [message #39904 is a reply to message #39789]

Fri, 10 May 2013 08:21

mirek
Messages: 14267
Registered: November 2005

Ultimate Member

piotr5 wrote on Sun, 28 April 2013 07:10

strange container, really. it stores N links to T where T is expected to be derived from Link. you could imagine it as N double-linked lists with each list-element being associated to a subset of those lists, and with each of those lists being connected back into a full loop. Interestingly only the 1st list gets destructed in the destructor of LinkOwner, guess this is the list that must contain all members. useful it is to represent different permutations of the same data. in uppsrc it is used only once, /home/p/upp/uppsrc/CtrlCore/CtrlTimer.cpp(22) for storing TimeEvent , and there N is set to 1 -- guess in future std::list could be used instead.

there actually is a bug in its implementation: it should be

template <class T, int N = 1>
class LinkOwner : public T {
public:
	~LinkOwner()                         { T::DeleteList(); }
};

otherwise compiling

template<typename T, int N=1>
class LinkElement : public Link<LinkElement<T,N>,N>
{
	public:
	T val;
};
LinkOwner<LinkElement<int,2> > delme;

(note that N is 2 here, with N=1 it would compile OK) will result in[code]


template <class T>
class LinkElement : public Link<LinkElement<T>, 2> {
public:
	T val;
};

LinkOwner< LinkElement<int>, 2 > delme;

is intended use and it works with current LinkOwner (and does not with proposed patch).

Other than that, I guess I can agree that Link is not the most important class in U++... Original idea was to simplify creation of multilinked lists, but the need for them diminished over time.

Mirek

Report message to a moderator