Class, Arrays, Operator overloading = instable code. Why?

[fx11]

Hi All!
I am a beginner to programming.
I learn C++ from site cplusplus.com.

I wanted to try operator overloading.
I wrote a C++ program using arrays.

I have now an instable code.
I don't know what's happening
but sometimes the code does what I want,
at other runtime it behaves strangely.


My C++ code was designed for this purpose:

1. Ask Length of Array A and B and C
2. Ask the Values of Array A and B
3. Length of C = Length of A + Length of B

4. Create a class CArray
5. Objects of this class get their values at initialization through constructors:
5.a. CArray obj(Array,Length) pass the Array and Length to the object
5.a. CArray obj(Length) pass the Length to the object
and create a Length length array filled with zeros.

6. Overload the operator ^
The operator function is a member of class CArray.
New meaning of operator ^
C=A^B concatenate the two arrays (A,B) into one (C).

Tutorials I used:
for Constructors and destructors
http://www.cplusplus.com/doc/tutorial/classes/
and
for Overloading operators
http://www.cplusplus.com/doc/tutorial/classes2/


INSATBLE RESULTS - WHY? I DON"T KNOW.

Any suggestion?


My Code:

// concatenate two arrays

#include <iostream>
using namespace std;

class CArray {
    public:
        int * cAry; int cLen;
        CArray(int conAry[], int conLen); CArray(int conLen); ~CArray();
        CArray operator ^ (CArray ritAry);
};

CArray::CArray(int conAry[], int conLen) {
    cLen = conLen; cAry = new int [conLen];
    for(int i=0;i<conLen;i++) cAry[i] = conAry[i];
}

CArray::~CArray() {
    delete [] cAry;
}

CArray::CArray(int conLen) {
    cLen = conLen; cAry = new int [conLen];
    for(int i=0;i<conLen;i++) cAry[i] = 0;
}

CArray CArray::operator^ (CArray ritAry) {
    int resLen=cLen+ritAry.cLen;
    CArray resAry(resLen);
    for(int i=0;i<cLen;i++)
        resAry.cAry[i] = cAry[i];
    for(int i=cLen,j=0;i<resLen;i++,j++)
        resAry.cAry[i] = ritAry.cAry[j];
    return (resAry);
}

void input4ary (int ary[], int lgth) {
    for(int i=0;i<lgth;i++) {
        cout << "ary["<<i<<"]= "; cin >> ary[i]; cout << "\n";
    }
    cout << "\n";
}

int main ()
{
    // input for array A
    int length_A; cout << "How many numbers do you want to type? ";
    cin >> length_A; cout << "\n";
    int * ary_A = new int [length_A]; input4ary(ary_A,length_A);

    // input for array B
    int length_B; cout << "How many numbers do you want to type? ";
    cin >> length_B; cout << "\n";
    int * ary_B = new int [length_B]; input4ary(ary_B,length_B);

    // length for array C
    int length_C; length_C = length_A + length_B;
    cout << "\n";

    CArray a(ary_A,length_A);
    CArray b(ary_B,length_B);
    CArray c(length_C);

    c = a ^ b;

    // Checking results

    cout << "Length of array of object a: " << (a.cLen) << "\n\n";
    cout << "Array of object a: \n\n";
    for(int i=0;i<(a.cLen);i++)
        cout << "a.cAry["<<i<<"]= " << (a.cAry[i]) << "\n";
    cout << "\n";

    cout << "Length of array of object b: " << (b.cLen) << "\n\n";
    cout << "Array of object b: \n\n";
    for(int i=0;i<(b.cLen);i++)
        cout << "b.cAry["<<i<<"]= " << (b.cAry[i]) << "\n";
    cout << "\n";

    cout << "Length of array of object c: " << (c.cLen) << "\n\n";
    cout << "Array of object c: \n\n";
    for(int i=0;i<(c.cLen);i++)
        cout << "c.cAry["<<i<<"]= " << (c.cAry[i]) << "\n";
    cout << "\n";

    return 0;
}

Tests on different IDEs:

Orwell Dev-C++ - Dev-Cpp 5.4.0 TDM-GCC x64 4.7.1 Setup.EXE
TDM-GCC 4.7.1 32bit

Sometimes it works as designed:

How many numbers do you want to type? 3

ary[0]= 1

ary[1]= 2

ary[2]= 3


How many numbers do you want to type? 2

ary[0]= 1

ary[1]= 4



Length of array of object a: 3

Array of object a:

a.cAry[0]= 1
a.cAry[1]= 2
a.cAry[2]= 3

Length of array of object b: 2

Array of object b:

b.cAry[0]= 1
b.cAry[1]= 4

Length of array of object c: 5

Array of object c:

c.cAry[0]= 1
c.cAry[1]= 2
c.cAry[2]= 3
c.cAry[3]= 1
c.cAry[4]= 4


Process exited with return value 0
Press any key to continue . . .

Sometimes it crashes:

How many numbers do you want to type? 5

ary[0]= 1

ary[1]= 2

ary[2]= 3

ary[3]= 4

ary[4]= 5


How many numbers do you want to type? 3

ary[0]= 6

ary[1]= 

AND THAT'S IT. HERE THE CODE CRASHES. 

Code::Blocks 12.11 - GNU GCC Compiler:

Sometimes it works as if it read wrong data:

How many numbers do you want to type? 3

ary[0]= 1

ary[1]= 2

ary[2]= 3


How many numbers do you want to type? 2

ary[0]= 1

ary[1]= 4



Length of array of object a: 3

Array of object a:

a.cAry[0]= 1
a.cAry[1]= 2
a.cAry[2]= 3

Length of array of object b: 2

Array of object b:

b.cAry[0]= 8654776
b.cAry[1]= 8650948

Length of array of object c: 5

Array of object c:

c.cAry[0]= 8655112
c.cAry[1]= 8654728
c.cAry[2]= 3
c.cAry[3]= 1
c.cAry[4]= 4


Process returned 0 (0x0)   execution time : 36.516 s
Press any key to continue.

Other test:

How many numbers do you want to type? 3

ary[0]= 1

ary[1]= 2

ary[2]= 3


How many numbers do you want to type? 2

ary[0]= 1

ary[1]= 4



Length of array of object a: 3

Array of object a:

a.cAry[0]= 1
a.cAry[1]= 2
a.cAry[2]= 3

Length of array of object b: 2

Array of object b:

b.cAry[0]= 8654776
b.cAry[1]= 8650948

Length of array of object c: 5

Array of object c:

c.cAry[0]= 8655112
c.cAry[1]= 8654728
c.cAry[2]= 3
c.cAry[3]= 1
c.cAry[4]= 4


Process returned 0 (0x0)   execution time : 36.516 s
Press any key to continue.

[Peter87]

The problem is when the objects are copied, it will just copy cAry and cLen to the new object so you end up with two objects having their cAry pointing to the same array. This will cause all kinds of problem.

Implement the copy constructor and copy assignment operator to make copying work the way you want.