memcpy strange

Here is the code:

Code:

---

   
        // set the array with values of 0
        for (int index = 0; index < NumElements -1; index++) {
                OriginalArray[index] = 0;
        }
       
        // forget about pure random at the moment
        for (int index = 0; index < NumElements -1; index++) {
                OriginalArray[index] = rand() % NumElements;
        }
 
    // stub for displaying numbers
        for (index = 0; index < NumElements -1; index++) {
            cout << OriginalArray[index] << '\t';
    }
       
    // copy the OriginalArray to the global RandomArray
    memcpy(RandomArray, OriginalArray, NumElements-1);
    cout << "\n\n\n\n";
   
    // stub for displaying numbers
        for (index = 0; index < NumElements -1; index++) {
            cout << RandomArray[index] << '\t';
    }

---

Here is some sample output:

Code:

---

6    4    3    9    6    4    1    0    6

// after 'copy'
6    4    3    0    0    0    0    0    0

---

What the? - rove

I cant figure out what is wrong, anyone see anything i cant?

> memcpy(RandomArray, OriginalArray, NumElements-1);
memcpy copies bytes, not ints
Try
memcpy(RandomArray, OriginalArray, sizeof RandomArray);

Thanks for the input, but that seems to make it worse, now only displaying 1 random number and following 0's. Is there a way to copy one element at a time and just loop it?

The third argument to memcpy is the number of bytes to copy so you want:

Code:

---

    memcpy(RandomArray, OriginalArray, NumElements * sizeof(RandomArray[0]));

---

I'm suspicious of your use of NumElements - 1. Typically we don't want the - 1 because we are using the < operator and therefore for an array with 5 elements we get:

Code:

---

        for (int index = 0; index < 5; index++) {
                // index goes from 0 to 4
                OriginalArray[index] = rand() % NumElements;
        }

---

while with - 1 we get:

Code:

---

        for (int index = 0; index < 5 -1; index++) {
                // Index goes from 0 to 3
                OriginalArray[index] = rand() % NumElements;
        }

---

> Thanks for the input, but that seems to make it worse, now only displaying 1 random number and following 0's.
See, I thought from your variable name that it was an array in scope and not just a pointer to an array :mad:

Thanks that works now, yes your right the -1 was not ment to be there, i copied a stub from somewhere else in the code nice job :) saved me lots of headaches.

edit: salem your on the money 99% of the time ill forgive you this once! ;)