Home » U++ Library support » U++ Core » the container type UPP::Link
| the container type UPP::Link [message #39789] |
Sun, 28 April 2013 13:10  |
piotr5
Messages: 107
Registered: November 2005
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Experienced Member |
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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 betemplate <class T, int N = 1>
class LinkOwner : public T {
public:
~LinkOwner() { T::DeleteList(); }
};
template<typename T, int N=1>
class LinkElement : public Link<LinkElement<T,N>,N>
{
public:
T val;
};
LinkOwner<LinkElement<int,2> > delme;/home/p/upp/uppsrc/Core/Other.h: In instantiation of ‘void Upp::Link<T, N>::Unlink(int) [with T = LinkElement<int, 2>; int N = 1]’:
/home/p/upp/uppsrc/Core/Other.h:275:76: required from ‘void Upp::Link<T, N>::UnlinkAll() [with T = LinkElement<int, 2>; int N = 1]’
/home/p/upp/uppsrc/Core/Other.h:288:51: required from ‘Upp::Link<T, N>::~Link() [with T = LinkElement<int, 2>; int N = 1]’
/home/p/upp/uppsrc/Core/Other.h:305:7: required from here
/home/p/upp/uppsrc/Core/Other.h:258:16: error: ‘LinkElement<int, 2>* Upp::Link<LinkElement<int, 2>, 2>::link_prev [2]’ is protected
T *link_prev[N];
^
/home/p/upp/uppsrc/Core/Other.h:273:64: error: within this context
void Unlink(int i = 0) { link_next[i]->link_prev[i] = link_prev[i]; link_prev[i]->link_next[i] = link_next[i];
^
/home/p/upp/uppsrc/Core/Other.h:259:16: error: ‘LinkElement<int, 2>* Upp::Link<LinkElement<int, 2>, 2>::link_next [2]’ is protected
T *link_next[N];
^
/home/p/upp/uppsrc/Core/Other.h:273:107: error: within this context
void Unlink(int i = 0) { link_next[i]->link_prev[i] = link_prev[i]; link_prev[i]->link_next[i] = link_next[i];
Edit: in case it wasn't clear, Link is connected in full circle back to itself, so iterating will eventually return to where you started...
[Updated on: Mon, 29 April 2013 00:43] Report message to a moderator |
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| Re: the container type UPP::Link [message #39904 is a reply to message #39789] |
Fri, 10 May 2013 08:21  |
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mirek
Messages: 14255
Registered: November 2005
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Ultimate Member |
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| 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 betemplate <class T, int N = 1>
class LinkOwner : public T {
public:
~LinkOwner() { T::DeleteList(); }
};
template<typename T, int N=1>
class LinkElement : public Link<LinkElement<T,N>,N>
{
public:
T val;
};
LinkOwner<LinkElement<int,2> > delme;
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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
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