Why do I have to add an assignment sign in C++ to declare an array?

Question

I have a question about the syntax in C++ when it comes to declaring arrays. I watched a tutorial where someone used the following code to create the array, but I get errors when running it.

It seems like I can only run the code if I include an = between the [] and the values of the array. Please explain why he doesn't get compiling issues as I did.

#include <iostream>

using namespace std;

int main(void) {
    char vowels[] {'a' ,'e', 'i', 'o', 'u' };

    cout << "\nThe first vowel is: " << vowels[0] << endl;
    cout << "The last vowel is: " << vowels[4] << endl;

    return 0;
}

Output:

main.cpp:10:10: error: definition of variable with array type needs an explicit size or an initializer

  char vowels[] {'a' ,'e', 'i', 'o', 'u' };
              ^
main.cpp:10:18: error: expected ';' at end of declaration

  char vowels[] {'a' ,'e', 'i', 'o', 'u' };
               ^

2 errors generated.

Why not just `const char* vowels = "aeiou";`? The end result is effectively the same, but with way less junk. — tadman, Jul 10 '20 at 18:36
@tadman Would be fine in this case, but that isn't exactly equivalent. In OP's case you could do `vowels[1] = 'x';` which doesn't work with your alternative. — François Andrieux, Jul 10 '20 at 18:38
@AndroYono Please share how you are compiling this. Which compiler, which version and which compilation flags are being used? — François Andrieux, Jul 10 '20 at 18:38
It seems your compiler or compilation mode is too old. Use compilers that support C++11 and enable C++11. — MikeCAT, Jul 10 '20 at 18:38
@FrançoisAndrieux I think it's fairly safe to presume that consonants are *constant*. — tadman, Jul 10 '20 at 18:38
The code you posted only becomes legal with C++11. You should enable that in your build. — john, Jul 10 '20 at 18:38
Why is the syntax of the language the way it is? Well, because that's the way it's defined. Like it or not. — Jesper Juhl, Jul 10 '20 at 18:39
[Why is “using namespace std;” considered bad practice?](https://stackoverflow.com/q/1452721/430766) — bitmask, Jul 10 '20 at 19:59

score 3 · Answer 1 · edited Jul 10 '20 at 18:59

3

The way you're trying to declare the array:

char vowels[] {'a' ,'e', 'i', 'o', 'u' };

is called extended initializer lists and it's only available from C++11 and above. Ensure your compiler supports this version and above. You may manually use -std=c++11 flag when compiling to verify (since it's not clear which version you're currently using to compile):

$ g++ -std=c++11 -o main main.cpp

Note: It'll work when you use an assignment operator = to assign it which is supported by old compilers:

char vowels[] = {'a' ,'e', 'i', 'o', 'u' };

edited Jul 10 '20 at 18:59

cigien

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answered Jul 10 '20 at 18:47

Rohan Bari

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Thank you! Is there any way I can set the default compiler version to c++11 without typing it in the comand line every time? – Andro Yono Jul 10 '20 at 19:09
1

@AndroYono Look into *makefiles* and/or CMake. – HolyBlackCat Jul 10 '20 at 19:10
1

It should be pointed out as well that there is no reason not to use `-std=c++17` instead of the much older C++11 revision. – bitmask Jul 10 '20 at 19:56

Why do I have to add an assignment sign in C++ to declare an array?

1 Answers1