vectors and fuctions

This is a discussion on vectors and fuctions within the C++ Programming forums, part of the General Programming Boards category; Code: #include<iostream> #include<vector> #include<string> using namespace std; void builtVector(string vectorName); //void sortVector(string vectorName); int main() { builtVector("v"); //sortVector(v); for(int i ...

  1. #1
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    vectors and fuctions

    Code:
    #include<iostream>
    #include<vector>
    #include<string>
    
    using namespace std;
    
    void builtVector(string vectorName);
    //void sortVector(string vectorName);
    
    int main()
    {
    	builtVector("v");
    	//sortVector(v);
    	for(int i = 0; i <= v.size(); i++)
    	{
    		cout << v[i];	
    	}
    	return 0;
    }
    
    vector<int> builtVector(final string vectorName)
    {
    	vector<int>	vectorName;
    	vectorName.push_back(4);
    	vectorName.push_back(2);
    	vectorName.push_back(7);
    	vectorName.push_back(1);
    	
    	return vectorName;	
    }
    
    --------------------Configuration: mingw2.95 - CUI Release, Builder Type: MinGW (Old)--------------------
    
    Compiling C:\Program Files\C-Free 4\temp\Untitled3.cpp...
    [Error] C:\Program Files\C-Free 4\temp\Untitled3.cpp:14: `v' undeclared (first use this function)
    [Error] C:\Program Files\C-Free 4\temp\Untitled3.cpp:14: (Each undeclared identifier is reported only once
    [Error] C:\Program Files\C-Free 4\temp\Untitled3.cpp:14: for each function it appears in.)
    [Error] C:\Program Files\C-Free 4\temp\Untitled3.cpp:21: parse error before `vectorName'
    
    Complete Compile C:\Program Files\C-Free 4\temp\Untitled3.cpp: 4 error(s), 0 warning(s)
    well I have some questions that have to do with some basic c++, but I cannot figure it out by myself so here I am.

    I use builtVector to initialize a vector, with param string vectorName; so when I call builtVector("v"); a vector v should be initialized. Anyway I get the above errors.
    Also if I have to return a vector should the return type of my fuction be vector or vector<int>???

  2. #2
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    1. There is no "final" keyword in C++

    2. vectorName is a string, not a vector.

    3. What book are you using to learn C++?

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    Code:
    int main()
    {
    	
    	builtVector();
    	//sortVector(v);
    	/*for(int i = 0; i < x; i++)
    	{
    		cout << v[i];	
    	}*/
    	return 0;
    }
    
    void builtVector()
    {
    	vector<int> v;
    	v.push_back(4);
    	v.push_back(2);
    	v.push_back(7);
    	v.push_back(1);
    	
    	return ;	
    }
    I modified it "a bit". The thing is I want to make a fuction with a parameter the vector's name and I have trouble making it. Can you help?

  4. #4
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    You either need to build the vector and return it, or pass it by reference or pointer.

    You should be learning with a book - these are very basic concepts.

    This one is free: Thinking in C++

  5. #5
    C++ Witch laserlight's Avatar
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    Are you trying to use pass by reference?
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  6. #6
    Confused Magos's Avatar
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    The name of the vector inside the function is irrelevant outside the function, so there is no need to pass a name like you do (naming vectors like that is not possible in C++ anyway).
    By naming, isn't this sufficient?:
    Code:
    std::vector<int> VectorName = BuildVector();
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    Code:
    int main()
    {
    	//sortVector(v);
    	vector<int> x = builtVector();
    	for(int i = 0; i < x.size(); i++)
    	{
    		cout << x[i];	
    	}
    	return 0;
    }
    vector<int> builtVector()
    {
    	vector<int> v;
    	v.push_back(4);
    	v.push_back(2);
    	v.push_back(7);
    	v.push_back(1);
    	
    	return v;	
    }
    Now I have this, and I am trying the pointer solution. I am having trouble though!!!

    You ment making a pointer pointing to the vector? Can you spoon feed me some code to work with???I already have the thinking in c++, I am just playing around now without the book.
    Last edited by mixalissen; 05-05-2008 at 09:51 AM.

  8. #8
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    I'd actually use a reference, and not a pointer. Sorry, spoon feeding is no fun - learn for yourself and you'll be much happier. If you have the book, look up references and passing function arguments by reference. You can figure it out. Post your first attempt at doing this.

  9. #9
    Confused Magos's Avatar
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    I wouldn't recommend jumping into pointers and references until you got the very basics first (like functions)
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  10. #10
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    ok first attempt to built with pointers

    Code:
    void  built(vector<int>* x);
    
    int main()
    {
    	vector<int> v;
    	built(&v);
    
    	return 0;
    }
    
    void built(vector<int>* x)
    {
    	*x.push_back(3);	
    	*x.push_back(4);
    	return ;
    }
    
    Compiling C:\Documents and Settings\mixalis\Επιφάνεια εργασίας\C++ applications\passing by pointer.cpp...
    [Error] C: request for member `push_back' in `x', which is of non-aggregate type `vector<int,allocator<int> > *'
    [Error] C:\: request for member `push_back' in `x', which is of non-aggregate type `vector<int,allocator<int> > *'
    the main idea is :
    Code:
    void foo(int* n)
    {
    	*n = 0;
    }
    
    void foo(int& n)
    {
    	n = 0;
    }
    
    int main()
    {
    	int n;
    	foo(&n);
    	return 0;
    }
    right???

    give some feedback. I swear I will study from the book and not continue misusing my time, jumping from example to example on the Internet ))))

  11. #11
    C++ Witch laserlight's Avatar
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    *x.push_back(3) is the equivalent of *(x.push_back(3)). What you want is (*x).push_back(3) or more commonly x->push_back(3).
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  12. #12
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    Great that's what I was looking for.But what about the get fuction?? How would your suggestion work on:
    Code:
    void get(vector<int>* y)
    {
    	for(int i = 0; i < y->size(); i++) (1)-----------
    	{
    		cout << &y[i];
    	}
    	
    	return;
    }
    This way I get the address of the variable not the variable stored there??? Any ideas???
    I hope (1) is correct. Thanx again

  13. #13
    C++ Witch laserlight's Avatar
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    This way I get the address of the variable not the variable stored there?
    You would use: (*y)[i].

    I hope (1) is correct.
    Almost. i should be a vector<int>::size_type, not an int.
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  14. #14
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    Thanx for that, really helpful, it took all afternoon but at least I learned something...

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