C++ expected constant expression

Question

#include 
#include 
#include 
#include 
#include 
using std::ifstream;
using namespace std;
         


        

Answer 1

You cannot have variable length arrays (as they are called in C99) in C++. You need to use dynamically allocated arrays (if the size varies) or a static integral constant expression for size.

Answer 2

The size of an automatic array must be a compile-time constant.

 const int size = 100;
 float x[size][2];

If the size weren't known at compile-time (e.g entered by the user, determined from the contents of the file), you'd need to use dynamic allocation, for example:

std::vector<std::pair<float, float> > x(somesize);

(Instead of a pair, a dedicated Point struct/class would make perfect sense.)