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const int num = 16;
struct inputs{
double X1[num];
double X2[num];
};
Gives me an error:
error: variably modified ‘X1’ at file scope
The same was true for 'X2'.
But I remember the above is fine for C++, the above is fine (I may be mistaken for C++).
Can anybody clarify this for me?
875
Arrays in C/C++ It is a group of variables of similar data types referred to by a single element. Its elements are stored in a contiguous memory location. The size of the array should be mentioned while declaring it.
Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.
To determine the size of your array in bytes, you can use the sizeof operator: int a[17]; size_t n = sizeof(a); On my computer, ints are 4 bytes long, so n is 68. To determine the number of elements in the array, we can divide the total size of the array by the size of the array element.
size is a variable, and C does not allow you to declare (edit: C99 allows you to declare them, just not initialize them like you are doing) arrays with variable size like that. If you want to create an array whose size is a variable, use malloc or make the size a constant.
I can point you to a C FAQ: I don't understand why I can't use const values in initializers and array dimensions.
What it basically says is that num isn't a true constant, it's just read-only. To get a true constant you would need a #define num 16.
Also on that page: C is unlike C++ in this regard.
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