Programming Forums - Arrays or Vectors?

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Arrays or Vectors?

I have seen a lot of debate on wheather to use arrays or vectors for passing arrays in functions. I have a simple program here that does not quite seem to work properly as what I intended. The goal is to take the arrays from f1() and f2() and pass all the elements to the main where the elements are added togethor. I get a "segmentation fault" error.

How would I use vectors as an alternate to arrays?



#include <iostream>

#include <cmath>

using namespace std;



double f1(int a);

double f2(int b);



int main()

{

        int a1, b1;

        double numTot[6];



        f1(a1);

        f2(b1);



        // sum of 2 arrays element by element

        for(int k=0; k<=5; k++)

        {

                numTot[k] = f1(a1) + f2(b1);

                cout << "numTot[" << k << "]: " <<  numTot[k] << endl;

        }

        return 0;

}



double f1(int a2)

{

        double num1[6];



        // place 6 numbers in array num1

        for(int t=0; t<=5; t++)

        {

                num1[t] = t+1.0;

                cout << "num1[" << t << "]: " << num1[t] << endl;

        }

        return num1[a2];

}



double f2(int b2)

{

        double num2[6];



        // place 6 numbers in array num2

        for(int j=0; j<=5; j++)

        {

                num2[j] = j+2.0;

                cout << "num2[" << j << "]: " <<  num2[j] << endl;

        }

        return num2[b2];

}

Thanks if anyone can clarify this.

:banana:

Use a pointer.
And pass the array through the function.

void func(double *table, int len)

The seg fault is caused by a1 and b1 being used to index an array before they have been initialized to a value within the valid range.

Here is a vector version of your code. I've not changed any logic, so if the output isn't what you expected, that's your fault:D

#include <iostream>

#include <vector>



using namespace std;



// TODO: Const correctness.



double f1(int a, double arg2);



int main()

{

        try

        {

                // a1 and b1 must be initialized to some number

                // withing the bounds of vecNum.

                int a1 = 0, b1 = 0;

                vector<double> vecNumTot( 6, 0 );



                f1( a1, 1.0 );

                f1( b1, 2.0 );

                

                // sum of 2 vector element by element

                vector<double>::iterator i = vecNumTot.begin();

                for( int j = 0; i != vecNumTot.end(); ++i, ++j )

                {

                        *i = f1( a1 , 1.0 ) + f1( b1, 2.0 );

                        cout << "vecNumTot[" << j << "]: " <<  *i << endl;

                }

        } catch ( std::out_of_range& )

        {

                // TODO: Error hadnling.

                

                // NOTE: This try/catch block isn't needed if

                // there's no chance a1/b1 are passed to

                // f1 with a value exceeding vecNum.end().

        }

        

        cin.get();

        return 0;

}



double f1( int a, double arg2 )

{

        vector<double> vecNum( 6, 0 );



        // place 6 numbers in int vector vecNum1

        vector<double>::iterator i = vecNum.begin();

        for( int j = 0; i != vecNum.end(); ++i, ++j )

        {

                *i = j + arg2;

                cout << "vecNum[" << j << "]: " << *i << endl;

        }

        

        // If 'a' is out of range, an exception will

        // be thrown.

        return vecNum.at( a );

}