is push_back() a overloaded function ?

This is a discussion on is push_back() a overloaded function ? within the C++ Programming forums, part of the General Programming Boards category; hi, is push_back() a overloaded function? bcoz, probabily push_back() accepts simple argument and also pointer both. is it a overloaded ...

  1. #1
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    is push_back() a overloaded function ?

    hi, is push_back() a overloaded function?

    bcoz, probabily push_back() accepts simple argument and also pointer both.

    is it a overloaded function ? if so, is there any other way acceptance rule ?
    blue_gene

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    unleashed alphaoide's Avatar
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    source: compsci textbooks, cboard.cprogramming.com, world wide web, common sense

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    ok,....it is written void push_back( const TYPE &val );

    so, pass by reference (alias).

    i have written a small code to see the behaviour...

    Code:
    #include<iostream>
    #include<vector>
    using namespace std;
    int main()
    {
    vector<int> z;
    int* p = new int[3];
    p[0]=6;
    z.push_back(p); // illegal
    z.push_back(p[0]); 
    cout<<z[0]<<endl;
    
    }

    Now suppose the vector contains array of pointers (say vector<int* > ) then how do i insert pointers into the vector ?? push_back() function wont allow me to enter pointer so whats the way to enter pointer into the vector ?
    Last edited by blue_gene; 05-01-2004 at 11:08 AM.
    blue_gene

  4. #4
    Registered User axon's Avatar
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    try this:
    Code:
    #include<iostream>
    #include<vector>
    using namespace std;
    int main()
    {
    	vector<int> z;
    	int* p = new int[3];
    	p[0]=6;
    	z.push_back(*p);  
    	cout<<z[0]<<endl;
    
    	return 0;
    }

    some entropy with that sink? entropysink.com

    there are two cardinal sins from which all others spring: Impatience and Laziness. - franz kafka

  5. #5
    Registered User axon's Avatar
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    it basically works the same way as if you would try to do this:

    Code:
    cout << p << endl;  //this wont give you an error on most compilers 
                                    //but will print out some gibberish
    
    cout << *p << endl; //if you do this, the program will print out the first element
                                     //of the array that p points to, hence, 6

    some entropy with that sink? entropysink.com

    there are two cardinal sins from which all others spring: Impatience and Laziness. - franz kafka

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    no that code was an example. my las question was not meant for that.

    forget about my code.



    my question > is it possible to create a vector<some_type *> ?? how do i insert pointers into the vector ?

    say i want to do something like....

    vector{ p1,p2,p3,p4} // where p1,p2,p3,p4...etc are pointers to something.

    is it possible ?

    i am learning . any help is appreciated.

    thanks
    blue_gene

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    unleashed alphaoide's Avatar
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    Code:
    #include<iostream>
    #include<vector>
    using namespace std;
    int main()
    {
        vector<int *> z;             // create a container for pointer to int
        int* p = new int[3];
        p[0]=6;
        z.push_back(p);             // push a pointer to int
        cout<< *z[0] <<endl;     // use * to print the value of int
    }
    source: compsci textbooks, cboard.cprogramming.com, world wide web, common sense

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    is it possible to create a vector<some_type *>
    Yes, and the syntax is just as you have it. Say you wanted to create a vector of pointers to int:
    Code:
    int num = 10;
    vector<int*> vec;
    vec.push_back(&num);
    Just remember that the regular warnings about pointers still apply. If they point to local variables, then they become invalid when the function exits. If they point to dynamically allocated memory, then you have to remember to free them when you are done.

    -tf

  9. #9
    carry on JaWiB's Avatar
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    I think it would be a problem trying to put an array of integers into a vector because it wouldn't know how large the array is. If you are using vectors you might as well do something like this:
    Code:
    #include<iostream>
    #include<vector>
    using namespace std;
    int main()
    {
    vector<vector<int> > z;
    vector<int> y;
    y.push_back(0);
    y.push_back(1);
    
    z.push_back(y); 
    
    cout<<z[0][0]<<endl;
    cout<<z[0][1]<<endl;
    
    }
    You might, however, be able to use a char array, provided it is null-terminated:
    Code:
    #include<iostream>
    #include<vector>
    using namespace std;
    int main()
    {
    vector<char* > z;
    char y[2];
    y[0]='a';
    y[1]='b';
    y[2]='\0';
    z.push_back(y);
    cout<<z[0]<<endl;
    cout<<z[1]<<endl;
    
    }
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

  10. #10
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    just a quick question by looking ur code.

    Code:
    int num = 10;
    vector<int*> vec;
    vec.push_back(&num); //  u r sending a pointer(address ) but push back demands alias  . pointer(here by using & ) and references are not same thing.
    blue_gene

  11. #11
    carry on JaWiB's Avatar
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    I believe alphaoide's solution will work...I wasn't thinking that the vector doesn't need to know the size, it just has the address of the first element in the array. You just need to dereference it or use the subscript operator as if you are working with an ordinary array.
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

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    >>I believe alphaoide's solution will work.....

    its giving compile error. i already checked that in my system . i copied and pasted.

    edit: i have ideas on ur example. i was curious to know how can i create vector<some_type *>.
    Last edited by blue_gene; 05-01-2004 at 11:56 AM.
    blue_gene

  13. #13
    unleashed alphaoide's Avatar
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    Quote Originally Posted by blue_gene
    >>I believe alphaoide's solution will work.....

    its giving compile error. i already checked that in my system . i copied and pasted.
    What compile error? It works on mine
    source: compsci textbooks, cboard.cprogramming.com, world wide web, common sense

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    g++ compiler....
    Last edited by blue_gene; 05-01-2004 at 12:09 PM.
    blue_gene

  15. #15
    unleashed alphaoide's Avatar
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    it works on both my vc++ 6.0 and g++
    source: compsci textbooks, cboard.cprogramming.com, world wide web, common sense

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