[MFC] vector-shift-left
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Thread: [MFC] vector-shift-left

  1. #1
    Join Date
    Aug 2009
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    [MFC] vector-shift-left

    Hello everyone!!!....

    I have a vector of n elements, and I'd want to shift it left, is there maybe a function that does it?...
    Like I have for example:

    1;2;3;4;5;6

    after shifting left I should have:

    2;3;4;5;6;7

    where I lost 1 and inserted 7 at last position...

    Thanks a lot
    Ciao
    Luigi

  2. #2
    Join Date
    Aug 2000
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    7,622

    Re: [MFC] vector-shift-left

    There is a function std::rotate() in <algorithm> (but you have to
    set the last element yourself). Here is an example using
    rotate with std::vector ... it also works with an array or CArray,
    \but the call will be slightly different:

    Code:
    std::vector<int> v;
    
    for (int i=0; i<6; ++i)
    {
       v.push_back(i+1);
    }
    
    std::rotate(v.begin(),v.begin()+1,v.end());
    v[5] = 7;

  3. #3
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    Re: [MFC] vector-shift-left

    There is no vector class in MFC, and no, there is no function to do that automatically. You need to do that manually.

    If you use a list, you can remove the first element and and one at the tail.

    If you use an array, you have to copy the elements, one by one, from i+1 to i, and then set the value you want for the last element.
    Marius Bancila
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  4. #4
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    Re: [MFC] vector-shift-left

    HI cilu.... I'm implementing a MFC DLL and I have vectors... i'm using VisualStudio 2008... so thanks to Philip Nicoletti for the std::rotate() hint...

    btw, Philip, your last name sounds italian... :-)

    Ciao,
    Luigi

  5. #5
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    Re: [MFC] vector-shift-left

    Quote Originally Posted by cilu View Post
    There is no vector class in MFC, and no, there is no function to do that automatically. You need to do that manually.

    If you use a list, you can remove the first element and and one at the tail.

    If you use an array, you have to copy the elements, one by one, from i+1 to i, and then set the value you want for the last element.

    There is a 'sort of' automatic way using MFC's CArray class. Store the first item, Delete the first item and add the former first to the end.
    Assuming int as type (should work for any type really).
    Code:
    int i = array[ array.GetUpperBound() ];
    array.RemoveAt(0);
    array.Add(i);

  6. #6
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    Re: [MFC] vector-shift-left

    Quote Originally Posted by npuleio View Post
    HI cilu.... I'm implementing a MFC DLL and I have vectors... i'm using VisualStudio 2008... so thanks to Philip Nicoletti for the std::rotate() hint...
    When you prefixed your title with [MFC] I made the assumption you talk about MFC containers, that don't feature a "vector". How could we figure that you mean std::vector when you didn't mention that at all? You should ask the questions correctly, without ambiguities.
    Marius Bancila
    Home Page
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    I do not offer technical support via PM or e-mail. Please use vbBulletin codes.

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