Function returning a function

This is a discussion on Function returning a function within the C++ Programming forums, part of the General Programming Boards category; Hello, I have a class using a hash table. The constructor of the hash table takes as parameters the number ...

  1. #1
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    Function returning a function

    Hello,
    I have a class using a hash table. The constructor of the hash table takes as parameters the number of buckets, a pointer to a hash function, and a pointer to a comparison function. My problem is that the size of the hashtable is not necessarily constant, so I can't define a function that takes into account the size of the hash table (i.e. my hash function would just mod the key by the size of the hashtable). Is there a way around this (e.g. creating a function that returns a function)?

  2. #2
    i dont know Vicious's Avatar
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    As long as the function returns the same type as the returnee

    Code:
    int ReturnMe ()
    {
        
        return number;
    
    }
    
    int GetReturnMe ()
    {
    
        return ReturnMe ();
    
    }
    I believe that works.
    What is C++?

  3. #3
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    I'm a little confused by what you mean? In C functions are not first-class, because you cannot return functions, only function pointers. But ordinarily you would store the table size along with the buckets, and you would, then, write functions using the tablesize.

  4. #4
    Registered User caroundw5h's Avatar
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    Quote Originally Posted by shawn_drn
    Hello,
    I have a class using a hash table. The constructor of the hash table takes as parameters the number of buckets, a pointer to a hash function, and a pointer to a comparison function. My problem is that the size of the hashtable is not necessarily constant, so I can't define a function that takes into account the size of the hash table (i.e. my hash function would just mod the key by the size of the hashtable). Is there a way around this (e.g. creating a function that returns a function)?
    Your questions seems a bit confusing. Are you wanting to dynamically allocate memory for the size of the hash Table? Regardless of the answers this is the wrong forum for your questions.

  5. #5
    ATH0 quzah's Avatar
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    Are you wanting to dynamically allocate memory for the size of the hash Table?
    That's what I was trying to figure out: Why they think they can't allocate a hash table dynamicly and return it. I'm not seeing where they're getting confused. Except for the minor point of them talking about constructors in the C forum.

    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
    Registered User Codeplug's Avatar
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    >> The constructor ... takes as parameters the number of buckets
    Isn't this the size of the table?

    >> problem is that the size ... is not necessarily constant, so I can't define a function that takes into account the size of the hash table
    The size of the hash table will be a member variable of the class. Since the size isn't constant, you'll have to create the table dynamically.
    You can pass around a dynamically created array by simply using a point to the array type. For example, "void foo(int *p)" can receive an int[100] or an int[1000] array.

    For future posts, use the C++ forum for C++ stuff.

    gg

  7. #7
    It's full of stars adrianxw's Avatar
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    Moved to C++ forum.
    Wave upon wave of demented avengers march cheerfully out of obscurity unto the dream.

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