length of array at runtime in C++

Question

I have been asked to prove that one can set the array length in the program, and it does not need to be determined at compile time. I have following code:

#include<iostream>
using namespace std;
int main()
{
    int x, myarray[x];
    cout << "Enter the size of array" << endl;
    cin >> x;
        }

But when I compile, I get the following errors:

error C2057: expected constant expression
 error C2466: cannot allocate an array of constant size 0
 error C2133: 'myarray' : unknown size

I'm not sure what the right way to approach it.

You can't prove that because array sizes have to be compile time constants. — chris, Oct 13 '14 at 15:34
What does `x` actually contain, when you say `myarray[x]`?!? — πάντα ῥεῖ, Oct 13 '14 at 15:36
***int x, myarray[x];*** Even if C++ had variable length arrays. You do realize that x is not initialized here.. — drescherjm, Oct 13 '14 at 15:37

score 1 · Answer 1 · answered Oct 13 '14 at 16:29

1

int matrix[x]; i dont think c++ does not support that kind of declaration. use new[] operator if you want to dynamically allocate memory for an array

answered Oct 13 '14 at 16:29

Abhijith P Haridas

135
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length of array at runtime in C++

1 Answers1