how to access array outside its scope

This is a discussion on how to access array outside its scope within the C++ Programming forums, part of the General Programming Boards category; here is a sample pseudo code of what i want to perform( i am using dev c++) Code: main() { ...

  1. #1
    Registered User
    Join Date
    Aug 2011
    Posts
    25

    how to access array outside its scope

    here is a sample pseudo code of what i want to perform( i am using dev c++)
    Code:
     main()
    {
      int r,c;
      cin>>r>>c;
      
      int a[r][c];
    }
    
    void f1()
    {
      ....
      ....
    }
    i want to access array a inside f1(). i can't pass array a as argument because then in the function prototype of f1 it will have to be of fixed size (like a[5][5]). so is there a way to access a inside other blocks. i tried :: operator but it won't work.

  2. #2
    Registered User
    Join Date
    Jun 2005
    Posts
    6,193
    No, the :: (scoping) operator cannot be used as you describe.

    Your creation of the array a is illegal in C++, anyway, so it's a moot point that you can't access it directly from f1(). And main() returns int.

    In C++, I'd use this (assuming f1() does not intend to change the passed information);
    Code:
    #include <vector>
    #include <iostream>
    
    void f1(const std::vector<std::vector<int> > &);
    
    int main()
    {
         int r,c;
         std::cin >> r >> c;
    
         std::vector<std::vector<int> > a(r, std::vector<int>(c));
    
         f1( a);
    }
    
    void f1(const std::vector<std::vector<int> > &a)
    {
        //   use a here
    }
    This is legal, as vectors carry their size information with them .... and so do vectors of vectors.
    Right 98% of the time, and don't care about the other 3%.

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