Re: [Toon-members] Re: STL containers with TooN

[E. Rosten]

On Tue, 12 Jan 2010, Gerhard Reitmayr wrote:

> Hi,
> On 11 Jan 2010, at 22:05, Gabriel Nützi wrote:
>
> > This code works:
> >
> > list<Vector<Dynamic,double> > la;
> >         la.push_back(makeVector(3,1,2,3,4));
> >         la.push_back(makeVector(3,1,3,4));
> >         la.push_back(makeVector(4,2,1,2,3,4));
> >         la.push_back(makeVector(4,3,4));
> >         la.push_back(makeVector(4,2,1,2,3,4,9,2,1));
> >         la.push_back(makeVector(3,1,2,3,4));
> >         la.push_back(makeVector(3,1,3,4));
> >         la.push_back(makeVector(4,2,1,2,3,4));
> >         la.push_back(makeVector(4,3,4));
> >         la.push_back(makeVector(4,2,1,2,3,4,9,2,1));
> >
> >         list<Vector<Dynamic,double> >::iterator it;
> >
> >         for(it = la.begin();it!=la.end();it++){
> >                 cout << *it <<endl;
> >         }
> >
> >         advance(it,8);
> >         it = la.erase(la.begin(),it);
> >         cout <<"erase"<<endl;
> >         for(it = la.begin();it!=la.end();it++){
> >                 cout << *it <<endl;
> >         }
> >
> > but the code from Gerhard, gives the fallowing error (resizable works):
> > /Users/gabrielnutzi/Desktop/TooNTest/TooN/internal/vbase.hh:96: error: no matching 
> > function for call to 'TooN::Internal::VectorAlloc<-0x00000000000000001, 
> > double>::VectorAlloc()'
> > /Users/gabrielnutzi/Desktop/TooNTest/TooN/internal/allocator.hh:167: note: candidates 
> > are: TooN::Internal::VectorAlloc<-0x00000000000000001, 
> > Precision>::VectorAlloc(int) [with Precision = double]
> > /Users/gabrielnutzi/Desktop/TooNTest/TooN/internal/allocator.hh:160: note:                 
> > TooN::Internal::VectorAlloc<-0x00000000000000001, Precision>::VectorAlloc(const 
> > TooN::Internal::VectorAlloc<-0x00000000000000001, Precision>&) [with Precision = 
> > double]
> >
> > What is the difference in allocation when it comes to a resizable ?
>
> most likely list.push_back uses a copy constructor (creates a new list element that 
> has as a member a Vector<Dynamic>) then the size is set at construction time 
> and everything works.
>
> push_back should not work for a vector as typically elements are already 
> allocated and constructed and only assigned...

They're allocated, but not constructed. I think they're generally 
constructed in-place with placement new, or whatever passes for that in an 
STL allocator.


> actually my code seems to fail, as there is no default constructor for 
> Vector<Dynamic>, is that right ?

That's correct.

> but another list implementation might work differently...

A passable solution is to use a vector<shared_ptr<Vector<> > >. Of course, 
C++0x will fix all our woes with its move constructors when it finally 
arrives...

-Ed

--
(You can't go wrong with psycho-rats.)(http://mi.eng.cam.ac.uk/~er258)

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