HELP!! Urgent !!

This is a discussion on HELP!! Urgent !! within the C++ Programming forums, part of the General Programming Boards category; Compile with Visual C++. At compile time, we may not know how many elements are need to be allocated. So, ...

  1. #16
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    Compile with Visual C++.

    At compile time, we may not know how many elements are need to be allocated.
    So, we would not know what array size to be defined. If that is the case, how are we going to dynamically allocate the array of pointers?

  2. #17
    CSharpener vart's Avatar
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    Why do you need an array? use vectors
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #18
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    Code:
    int* someData;
    
    //at one point you know how many elements you need
    someData = new int[ELEMENTS];
    
    //fill the array
    delete [] someData;

  4. #19
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    There are few if any reasons to use the dynamic array in indigo0086's example over a vector. This does basically the same thing as that. You can also use functions like push_back or resize to make things easier on yourself.
    Code:
    vector<int> someData(ELEMENTS);

  5. #20
    Frequently Quite Prolix dwks's Avatar
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    1 quick question:
    Code:
    menuItem_t **ptr_1;
    and
    Code:
    menuItem_t *ptr_1[];
    Are they the same?
    As you might have guessed, but no one's actually said, the second one shouldn't compile. Unless it's a parameter to a function, in which case both of those code samples are the same. After all, this
    Code:
    int main(int argc, char *argv[])
    is the same as this
    Code:
    int main(int argc, char **argv);
    dwk

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  6. #21
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    Quote Originally Posted by indigo0086 View Post
    Code:
    int* someData;
    
    //at one point you know how many elements you need
    someData = new int[ELEMENTS];
    
    //fill the array
    delete [] someData;

    What if the data type is a structure?for eg: menuItem_t
    Is the below definition correct?
    Code:
    menuItem_t **someData;
    
    someData = new (*menuItem_t)[MAXSIZE];
    
    delete [] someData;

  7. #22
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    There are still few if any good reasons to go this route rather than use a vector, but if you are more comfortable with it (or the other person is making the decision) then the syntax would be:
    Code:
    menuItem_t **someData;
    
    someData = new menuItem_t*[MAXSIZE];
    
    // later, when you are done:
    delete [] someData;
    However, using MAXSIZE for the size of the array is something you usually do with static arrays, not dynamic ones. You would use the same code you had above with the 5, but instead of 5 you would use a constant like MAXSIZE.

    If MAXSIZE is not constant, then the code I just posted would work. Remember also that the pointers aren't initialized, so you'll have to do that yourself.

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