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

[Gerhard Reitmayr]

On 13 Jan 2010, at 18:37, E. Rosten wrote:

> On Wed, 13 Jan 2010, Gerhard Reitmayr wrote:
> 
>>> just from reading docs, one needs default, copy constructors and assignment 
>>> to work. that makes sense for example with the following code:
>>> 
>>> vector<Vector<Dynamic> > v(10); // 10 dynamic vectors
>>> v[0] = Vector<Dynamic>(10);     // set first to a vector with 10 els
>>> v[1] = Vector<Dynamic>(20);     // set second to a vector with 20 els
>>> 
>>> Resizable makes sense, i guess that assignment on a Resizable should always 
>>> work (and resize as necessary)
> 
> Ok. Presumably then it should also resize on assignment from a sized 
> operator, eg:
> 
> Vector<Resizable> v;
> v = Zeros(10);
> v = Zeros(20);
> 

yes, I think so

> 
>>> For Dynamic, how about making it stateful and have the default constructor 
>>> set a sentinel that allows it to be resized with the first assignment ? 
>>> (and assert, if it is assigned from another Dynamic in the same state )? a 
>>> copy constructor or explicit size constructor will not allow further 
>>> resizing, similarly after the first resize. that way the code above would 
>>> work and one would still have the same runtime safety...
>>> 
>> 
>> 
>> just got bitten again by the missing default constructor for 
>> Vector<Dynamic>. How about the above suggestion ? this we could have them 
>> default constructed and fixed on first assignment ?
> 
> That could work. Either my_data could be NULL or my_size equal to 0 or 
> something. Of course, then they have to be non-const. I don't know if that 
> matters much. I suspect not.
> 
> By the way, this would of course mean there will be an extra if in each 
> assignment from vectors or operators.
> 

ok, I understand that. but there is one already for the size mismatch I assume ?

> I implemented such a system for Vector<Resizable> which I subsequently 
> removed.
> 
> cvs up -D 20090926
> 
> should get you there. Each allocator implements a try_resize() member. This 
> may do nothing (for static and Dynamic), or it may do something 9for 
> Resizable). This member is called at the beginning of operator=. Then the 
> size checks occur. This system could be reinstated so that try_resize works 
> first time on Vector<Dynamic> and is a noop all other times.
> 
> 
> However, STL vector can call operator=
> 

that is true... in this case the Dynamic solution doesn't make sense. Probably 
forget it and make Resizable assignable, then that should be used. that looks 
like the best solution to me right now :/

cheers,
  Gerhard

> #include <vector>
> #include <iostream>
> using namespace std;
> 
> struct Foo
> {
>       Foo()
>       {}
> 
>       Foo(const Foo&)
>       {
>               cout << "copy\n";
>       }
> 
>       Foo& operator=(const Foo&)
>       {
>               cout << "assign\n";
>               return *this;
>       }
> };
> 
> 
> int main()
> {
>       vector<Foo> v(3);
>       cout << "Erase\n";
>       v.erase(v.begin());
> }
> 
> 
> prints out:
> copy
> copy
> copy
> Erase
> assign
> assign
> 
> If Vector<Resizable> supported resize on assignment as it used to, then I 
> think it would be OK to use in a std::vector.
> 
> -Ed
> 
> 
>> cheers,
>> Gerhard
>> 
>>> cheers,
>>> Gerhard
>>> 
>>>> Thoughts, anyone?
>>>> 
>>>> -Ed
>>>> 
>>>> 
>>>> 
>>>>> Thanks!
>>>>> 
>>>>> Am 10.01.2010 um 21:37 schrieb Gabriel Nützi:
>>>>> 
>>>>>> Hello again
>>>>>> Sorry for my questions, but I am using TooN permanently, with all its 
>>>>>> advantages... (LU,SymEigen....)
>>>>>> I was wondering, because I need a container which is as fallowing
>>>>>> list < Vector<Dynamic,double> >   myList;
>>>>>> Why does it give RunTime problems and segmentation errors when I try to 
>>>>>> use the list by inserting and deleting Vectors, it happens also when the 
>>>>>> Vector is not dynamic ...
>>>>>> Is there any troubles with the containers and TooN?
>>>>>> This crashed in Runtime:
>>>>>> //===================================
>>>>>> list < Vector<Dynamic,double> >   myList;
>>>>>> myList.push_back( makeVector (1,1,1) );
>>>>>> myList.push_back( makeVector (2,1,1) );
>>>>>> myList.push_back( makeVector (3,1,1) );
>>>>>> list < Vector<Dynamic,double> > ::iterator it;
>>>>>> it = myList.begin();
>>>>>> it++;
>>>>>> myList.erase(it);
>>>>>> //=================================
>>>>>> Thanks a lot
>>>>>> Gabriel!
>>>>> 
>>>>> 
>>>>> 
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--
Gerhard Reitmayr
Institute for Computer Graphics and Vision
http://www.icg.tugraz.at/Members/gerhard
tel: ++43 316 873 5082