Why Does Initializing a C Array with a Variable Size Result in an Error?

Array[n] vs Array[10]: Initializing Arrays with Variable vs Numeric Literal

In C , an error occurs when initializing an array with a variable as its size, as seen in the code below:

int n = 10;
double tenorData[n] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

The error is: "variable-sized object 'tenorData' may not be initialized." This is because variable-sized arrays are not allowed in C .

G allows this behavior as an extension, but it is not technically compliant with the C standard. To fix this issue, one can either dynamically allocate memory or use standard containers.

Dynamic Memory Allocation

int n = 10;
double* a = new double[n];

Remember to free the allocated memory using delete [] a; when finished.

Standard Containers

int n = 10;
std::vector<double> a(n);

Constant Arrays

If a proper array is desired, it can be initialized with a constant value rather than a variable:

const int n = 10;
double a[n];

In C 11, a constexpr can be used when obtaining the array size from a function:

constexpr int n()
{
    return 10;
}

double a[n()];

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