Question

I have a static size array of length 1, which I try to assign a value at index 0.

void main() {
   int length = 0;
   int[1] arr;

   arr[0] = 1;
   arr[length] = 2;
}

With the above code, I get a runtime error of

Error: ArrayBoundsError array.d(6)

which cooresponds the line: arr[length] = 2.

Why does the constant 0 work, but the variable with value 0 not work?

Answer 1

length has a special meaning inside index/slice expressions – it does the same thing as $ (the length of the array being indexed/sliced). Thus, arr[length] will always result in an ArrayBoundsError.

Note: length is deprecated in D2, and both D1 and D2 will issue a warning (when warnings are enabled): array 'length' hides other 'length' name in outer scope.