Question

I’m trying to create a dynamic memory. The size of the array is determine by the user input. I’m getting the following error,
"expression must have a constant value".

it seems like I’m doing something wrong. Please help me! How can I make this dynamic?

This is what I have so far:

int* IntPtr = NULL;
int main(){

 int arraySize;
 cout << "How many numbers will be on the list? ";
 cin >> arraySize;

 IntPtr = new int[arraySize];

Contact list[arraySize]; // <-- expression must be constant

//more code

delete [] IntPtr;

Answer 1

You’re trying to use Variable Length Arrays. Unfortunately, C++ does not allow them. (though some compiles allow them by extension)

What you need instead is to dynamically allocate the array using new. (and manually deallocate later with delete)

You’re already doing this correctly with:

IntPtr = new int[arraySize];

Now you can do the same with the list variable:

Contact *list = new Contact[arraySize];
delete [] list;

Alternatively, you can use the vector class, which is often preferred over dynamic arrays.

vector<Contact> list(arraySize);