Thread: Why use [3] when first is [0]?

  1. #1

    Why use [3] when first is [0]?

    If you need 3 things stored in an array why is it that so many people use an array of [3] when the first is [0]? Wouldn't you only need [2]?
    for example
    float m_location[3];
    That is used to store the x, y, and z coordinates of a vertex. However, I do not see why
    float m_location[2];
    wasn't used instead. Can someone shed some light on this topic?

  2. #2
    Registered User
    Join Date
    Dec 2001
    if it's a character array, then the last space is taken up by a null terminator (I think that's the correct name). it's represented as \0.

    so if I wanted to store "dog" in char array[3], the memory would look like this:

    Array Position:   0     1     2     3
    Character:        D     O     G     \0
    other than that, I think people just forget that arrays start at 0. I'm probably wrong though.

  3. #3
    TransparentMember correlcj's Avatar
    Join Date
    Jun 2002

    Your right!

    See similar code the face master produced earlier and see.
    I see because it starts at 1 instead of 0 as i to think.

    #include <iostream>
    using namespace std;
    int main()
    int array[10];
    for(int i = 10; i > 0; i--)  //this is set to 1 instead of 0
        array[i] = i;
    // just to check its all been done properly...
    for(int j = 10; j > 0; j--)
        cout << array[j];
        cout << "\n";
    return 0;
    Is this what you mean?

    null terminator (I think that's the correct name).
    Yes, your correct.
    "Be formless, shapeless, like water... You put water into a cup, it becomes the cup, you put water into a bottle, it becomes the bottle, you put it in a teapot, it becomes the teapot... Now water can flow, or it can crash, be water my friend."
    -Bruce Lee

  4. #4
    When you declare an array the number is the total indices and not the maximum count.

    int array[3];

    equals ...

    array[0] , array[1], array[2];

    If you said...

    int array[2]; // Then it's only

    array[0], array[1];

    //The maximum [val] is (n-1) so int array[7]; would be array[0] through array[6]
    Last edited by OneStiffRod; 11-08-2002 at 07:04 PM.
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  5. #5
    Registered User
    Join Date
    Nov 2002
    okay, when you first declare the array, int array[3] reserves memory for 3 arrays, index numbers of 0, 1, 2. when you refer to them after declaration, then they are refered to by index number, but the declaration tells the computer how many slots you want in your array.

    edit: beaten.

  6. #6
    Yes I knew that aboiut character arrays, but I am talking about arrays of virtually every other data type. I always see people use :
    float mp_verticies[3]
    cat listofcats[3]
    CVector3 LineNormals[3]
    when three instances of each are all that is needed, yet enough space is set aside for 4

  7. #7
    int array[3] reserves memory for 3 arrays
    You mean an array of 3 instances of its type

  8. #8
    ok well onestiffrod answered it, if he is correct he confirmed what i thought

    sorry for the triple post

  9. #9
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    Apr 2002
    He's correct.

    "When the only tool you own is a hammer, every problem begins to resemble a nail." Abraham Maslow

  10. #10
    Registered User
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    Nov 2002
    Originally posted by Shadow12345
    You mean an array of 3 instances of its type
    yes, i typed it too fast to notice what i typed.

  11. #11
    Registered User
    Join Date
    Sep 2002
    array[0] must be blank im pretty sure of this.

  12. #12
    geek SilentStrike's Avatar
    Join Date
    Aug 2001
    array[0] is NOT blank. It's the first valid element in the array.
    Prove you can code in C++ or C# at TopCoder, referrer rrenaud
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  13. #13
    S Sang-drax's Avatar
    Join Date
    May 2002
    Göteborg, Sweden
    Originally posted by niroopan
    array[0] must be blank im pretty sure of this.
    You are?
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  14. #14
    lol maybe everyone should google arrays and read

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