pointers for dynamic 2D arrays
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Thread: pointers for dynamic 2D arrays

  1. #1
    Join Date
    Aug 2007
    Posts
    3

    pointers for dynamic 2D arrays

    hi. i am wanting to know how to make a 2d dynamic array.

    if i typically compiled :

    int row = 2;
    int column = 3;

    int a[row][column];

    That would cause an error in comilation saying non constant array bounds


    But, for the 1D case,I can overocme this by :

    int * ptr = NULL;
    int row;
    cin >> row;
    ptr = new int[row];

    That will create a dynamic array where ptr points to the first element/


    But when I try this for the 2D case, it doesnt work. THe prototype for the 2D case would be:

    int row;
    int column;
    int * ptr = NULL;
    cin >> row;
    cin >> column;
    ptr = new int[row][column];


    This would be the prototype ; i.e. for other datatypoes i just switch int with what i want.



    In my case, I have a custom datatype:

    class Pixel
    {
    char r;
    char g;
    char b;;
    }

    I then got rows and columns into variable unsigned integer rows, and unsigned integer columns

    Then I created:

    Pixel * ptr = NULL;

    This works: ptr = new Pixel[rows] ;



    But this does not work: ptr = new Pixel[rows][columns]; visual c++ gives :

    error C2540: non-constant expression as array bound

    and

    error C2440: 'initializing' : cannot convert from 'Pixel (*)[1]' to 'Pixel *'




    HEPL PLEASE

  2. #2
    Join Date
    Aug 2007
    Posts
    3

    Re: pointers for dynamic 2D arrays

    just realized that i should have used the search function to see if this topic qwas already done before. sorry if it has been just realized this havent poste din a long time./

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