I still need help on this!

This is a discussion on I still need help on this! within the C++ Programming forums, part of the General Programming Boards category; How do I initialize my templated array class?? So let's say my template class is this... template <class T> class ...

  1. #1
    Registered User adonisv's Avatar
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    I still need help on this!

    How do I initialize my templated array class??

    So let's say my template class is this...

    template <class T>
    class RArray {
    private:
    typedef enum { StartArraySize = 128} bogus;
    typedef enum {InitialSize = 0};

    size_t num_elem;

    size_t array_size;

    size_t array_Cursor;

    T *pArray;


    private:

    public:


    I can add an init routine like this?


    RArray()
    {
    pArray = new T[ StartArraySize ];
    num_elem = InitialSize;
    array_Cursor = InitialSize;
    array_size = StartArraySize;
    }


    Like this?

    void Init()
    {
    int i = 0;
    for (;i< StartArraySize;i++)
    {
    pArray[i] = 0;
    }
    pArray
    }



    ~RArray()
    {
    if (pArray != NULL) {
    delete [] pArray;
    }
    }
    Last edited by adonisv; 02-19-2003 at 05:23 PM.

  2. #2
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    code tags, and more descriptive title.

  3. #3
    samurai warrior nextus's Avatar
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    pretend i have this..(example)

    Code:
    template<class t>
    class test
    {
    public:
    test();
    int somefunction();
    };
    
    // to define it outside the class you need to do this
    template<class t>
    test<t>::test()
    {
    //default constructor..whatever you want!
    }
    
    template<class t>
    int test<t>::somefunction()
    {
    //still whatever you want
    }
    hope that helps
    nextus, the samurai warrior

  4. #4
    samurai warrior nextus's Avatar
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    also did you know you can do this?

    Code:
    template<class t, int num> //<---look at that
    class test
    .
    .
    .
    .
    //in the constructor
    template<class t, int num>
    test<t, num>::test()
    {
    pArray = new t[num]; // the person can make array any size they want
    ...
    ..
    }
    
    int main()
    {
    test<int, 20> array; //wow array of 20
    
    return 0; // very famous
    }
    nextus, the samurai warrior

  5. #5
    samurai warrior nextus's Avatar
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    also your class definition is just like a "blue print" so you can not initialize anything in the class, but you can assign it stuff in the constructor etc..or other functions...instead of using

    Code:
    void Init()
    put the body of that function in the constructor...much better
    nextus, the samurai warrior

  6. #6
    Registered User adonisv's Avatar
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    Unhappy

    So I can't have an initializaton routine IN the class? I'm so confused....

  7. #7
    samurai warrior nextus's Avatar
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    you sorta can..its in the constructors..look

    you cant do this
    Code:
    class test
    {
    private:
    int number = 5;
    };
    nope wrong!

    but you can do this
    Code:
    class test
    {
    private:
    int number;
    public:
    test(int x = 5): number(x) {}
    };
    
    // or
    class test
    {
    private:
    int number;
    public:
    test(int x = 5)
    {
    number = x;
    }
    };
    now you get it?
    nextus, the samurai warrior

  8. #8
    Registered User adonisv's Avatar
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    Cool

    I guess what confuses me is that since my template is generic and is supposed to take any "type" that I pass it, how would I set all of its initial elements to NULL or zero or whatever? Is this even a good idea for a template since I will be overwriting the entries eventually anyway?
    Logic, Reason and Creativity...

  9. #9
    samurai warrior nextus's Avatar
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    the almighty beautiful "for" loop and set it equal to 0;
    and i think NULL is another keyword for 0 (really means same i think...i read it somewhere in my book or so)

    so
    Code:
    int* pnum = NULL;
    int* pnum2 = 0; //both points to nothing
    hehe..hope that helps
    nextus, the samurai warrior

  10. #10
    Registered User adonisv's Avatar
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    Question

    RArray()
    {
    int i = 0;
    num_elem = num;
    array_Cursor = sizeof(0);
    pArray = new T[num];

    for(;i<num;i++)
    {
    pArray[i] = array_Cursor;
    //also with 0 or NULL
    }

    }
    My compiler says the equal operator is ambiguous...


    --------------------Configuration: ADOXperiment - Win32 Debug--------------------
    Compiling...
    ADOXperiment.cpp
    d:\data\vss\coderesearch\adoxperiment\debug\msadox .tlh(1201) : warning C4146: unary minus operator applied to unsigned type, result still unsigned
    d:\data\vss\coderesearch\adoxperiment\debug\msado1 5.tlh(409) : warning C4146: unary minus operator applied to unsigned type, result still unsigned
    d:\data\vss\coderesearch\adoxperiment\rarray.h(85) : error C2593: 'operator =' is ambiguous
    d:\data\vss\coderesearch\adoxperiment\rarray.h(75) : while compiling class-template member function '__thiscall RArray<class _variant_t,100>::RArray<class _variant_t,100>(void)'
    Error executing cl.exe.

    ADOXperiment.exe - 1 error(s), 2 warning(s)
    Logic, Reason and Creativity...

  11. #11
    samurai warrior nextus's Avatar
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    what is num equal to? your didnt put anything in your constructor to take values

    RArray()

    .....think of the constructor as a regular function
    also..pArray[i] = 0; // good enough dont use sizeof(0)
    nextus, the samurai warrior

  12. #12
    Registered User adonisv's Avatar
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    I don't need to with this syntax my code is smaller

    template <class T, int num>
    class RArray {
    ....

    I called it this way

    // Create instance of the templated array class. Establish that
    // it will be holding _variant_t data types.

    RArray< _variant_t,100 > BookMarks;

    Compiler says ok and it runs....
    Logic, Reason and Creativity...

  13. #13
    Registered User adonisv's Avatar
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    Exclamation Compiler no likey likey...

    RArray()
    {
    int i = 0;
    num_elem = num;
    array_Cursor = sizeof(0);
    pArray = new T[num];

    for(;i<num;i++)
    {
    pArray[i] = 0;
    }

    }

    Logic, Reason and Creativity...

  14. #14
    samurai warrior nextus's Avatar
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    well what value you get for num..did you past it into the RArray(int num) or was it defined in your class

  15. #15
    Registered User adonisv's Avatar
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    I passed it a "num" when I declared it in the function where it's used..

    int ArchiveTable(const char* copiedTableName,const char* alsoCopiedTable,const char* dataSource)
    {
    // Return negative one if table name and datsource are null.
    if (!copiedTableName || !dataSource || alsoCopiedTable)
    return -1;

    // Declare and initialize local variables.
    bool bSuccessful = false;
    enum DataTypeEnum columnType = adDate;
    long columnCount = 0;


    // Define ADOX variable types.
    HRESULT hr = S_OK;
    _bstr_t columnName;
    _variant_t vIndex;
    _variant_t vNull;



    // Create instance of the templated array class. Establish that
    // it will be holding _variant_t data types.

    .... RArray< _variant_t,100 > BookMarks;

    other fun stuff
    Logic, Reason and Creativity...

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