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Crayon Shin Chan
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### More trouble with iterators, multidim deques

This following code works perfectly:
``   (in the header file)   deque<deque<deque<int> > > openlist;   deque<deque<deque<int> > >::iterator openlist_Iterator;(in the cpp file)for(int i=-1;i<=1;i++) //For the 8 surrounding pixels around some pixel (initially startPixel), find white pixels and add them to open list   {      for(int j=-1;j<=1;j++)      {         currentcolor=image.pixel(currentPixel[0]+i,currentPixel[1]+j);         if(qGreen(currentcolor)==g && qRed(currentcolor)==r && qBlue(currentcolor)==b)         {            openlist[0][0].push_back(currentPixel[0]+i); //openlist[0] is the position of the pixel on the open list            openlist[0][1].push_back(currentPixel[1]+j);            openlist[1][0].push_back(currentPixel[0]); //openlist[1] is its parent pixel            openlist[1][1].push_back(currentPixel[1]);            if((i==0 || j==0) && !(i==0 && j==0))//openlist[2][0] is the G cost               {openlist[2][0].push_back(10);}            else               {openlist[2][0].push_back(14);}            openlist[2][1].push_back(manhattan());//openlist[2][1] is the H cost         }      }   }``

The only reason I'm using iterators is to try out something new. According to http://www.cprogramming.com/tutorial/stl/iterators.html the following works:
``for(myIntVectorIterator = myIntVector.begin();         myIntVectorIterator != myIntVector.end();        myIntVectorIterator++){    cout<<*myIntVectorIterator<<" ";    //Should output 1 4 8}``

But actually this doesn't? WTF? VS2003 gives me an error C2100 about not being able to dereference something that isn't a pointer. I don't know how else to do this.
``   for(openlist_Iterator=openlist.begin();openlist_Iterator!=openlist.end();openlist_Iterator++) //find the lowest F cost square   {      (*openlist_Iterator[2][0])+(*openlist_Iterator[2][1]);   }``

Are the new features in C++ supposed to be THIS hard to learn? BTW I have no clue how to traditionally (C array style) access the xth element of a 3D deque, where an element of the 3D array in this program's case has 6 values.
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mboza
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### Re: More trouble with iterators, multidim deques

``   for(openlist_Iterator=openlist.begin();openlist_Iterator!=openlist.end();openlist_Iterator++) //find the lowest F cost square   {      (*openlist_Iterator)[2][0]+(*openlist_Iterator)[2][1];   }``

not sure exactly what you are trying to do, but [] is higher precedence than *, and the iterator doesnt have a [] operator, hence the compile error.

Is this a 3D array - do you have openlist[i][j][k], or are the first two indices just 0-2 and 0-1? I would suggest something like

``struct foo{int posi, posj, parenti, parentj, Gcost, Hcost//or int pos[2], parent[2], Gcost, Hcost};deque<foo> openlist``

and then
``for(openlist_Iterator=openlist.begin();openlist_Iterator!=openlist.end();openlist_Iterator++) //find the lowest F cost square   {      openlist_Iterator->Gcost + openlist_Iterator->Hcost   }``

or perhaps:
``deque<int> posi, posj, parenti, parentj, Gcost, Hcost``

because I don't see the 3D-ness of your array - you have a list (or deque) of pixels, and a fixed number of properties associated with each pixel, so either organise these properties together and have a list of structs, or have a struct of lists, which might be more efficient if you are iterating over the properties independently of each other, or might not be.

Crayon Shin Chan
Minister of Gerbil Affairs
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Posts: 2295
Joined: Fri Sep 06, 2002 11:14 am
Location: Malaysia
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### Re: More trouble with iterators, multidim deques

Thanks, you're right... a struct would be a better fit. Anyway the rules have changed, and I've scrapped the code anyway. Thanks, I learned about structs and how other people use them.
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