Question

Hi I have a text file containing two arrays and one value(all integers)
like this

3 90 22 5 60 33 24

Where the first number stands for how many integers to read in.
I can read in all this in one function.
Do I need several functions to be able to use the different matrices and the first variable?

    ifstream in(SOMEFILE.dat);
    if (!in) {
    cerr << "Cannot open file.\n";
    return -1;}
    in >> VAR;
    A=new int[VAR]; 
    B=new int[VAR];
    for(int i=0 ;i<VAR;i++){
      in >>A[i];
    }
 for(int i=0 ;i<VAR;i++){
      in >>B[i];
    }

       in.close();

Above is the code I have so far and this would work in the main function.
Do I have to write three functions to read this info in so I can use it in my program or is there any way I could for example send in three pointers to a function?

I would like A to be 90 22 5
B to be 60 33 24
And VAR to be 3

Thanks

Answer 1

Whenever you want to group together data items, use a class or a structure. For example, to pass three integers as x, y and z coordinates,:

struct Coord {
   int x, y, z;
};

and then pass the structure to the function:

void f( Coord & c ) {
}

The same goes for arrays, but in your case you would make the structure contain pointers.

Your question actually opens up huge areas of C++ programming that it seems you are not aware of. Some things you should read up on before you go any further:

• the concept of structures, as outlined above
• constructors and destructors for structures
• when and when not to use dynamic memory allocation
• use of C++ standard library containers like std::vector

This may seem a lot, but once you have a clear grip on these, you will find C++ programming much, much easier and safer.