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c++arraysinitialization
kadina
kadina

Reputation: 5384

Array declaration with const expression

I am trying to declare an array with const value globally as below. But it is giving compilation error saying array size is not a const value.

const int a[] = {1, 2, 3, 4, 5};

int arr[a[1]];

But if I copy the same lines into a function, it is working fine.

Can you please let me know the differences and why it is not working when I tried to declare global array.

Upvotes: 3

Views: 800

Answers (1)

Vlad from Moscow
Vlad from Moscow

Reputation: 310980

If your compiler supports the new specifier constexpr of the C++ 2011 Standard then try

constexpr int a[] = {1, 2, 3, 4, 5};

int arr[a[1]];

As for the compiling your code when it is placed in a function then such a code is not C++ compliant. It is a language extension of the compiler you are using. The size of the array shall be a constant expression known at compile time.

In C you may use Variable Length Arrays (VLA). Some copilers included this feature of the C Standard in C++.

Upvotes: 4

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