6 ms·

I think I might disagree with #3. I find that having arr[-1] point towards the last element of the array can hide accidental off-by-one errors. It's also a bit

• Spartan-S63 6y ago
  If your mental model is that an array is zero-indexed but circular, I think arr[-1] still is consistent with that model. If you don’t think of arrays as circular, then sure, it doesn’t make sense. I’m still in agreement that negative indices make it more confusing than just calculating based off the length, but I get why they exist.
  • jniedrauer 6y ago
    You can also think of negative indexes as a shorthand for length-N. arr[-1] is the same as arr[len(arr)-1].
  • ironmagma 6y ago
    The mental model doesn’t really jive with circularity since arr[arr.length] is not the same as arr[0] in any language that I know of. With a circle, you would expect that arr[0], arr[length], and arr[2*length] are all identical.
• gizmo686 6y ago
  Certainly negative indexes being out-of-bounds would be the most consistent behaviour, but that requires giving up the index-from-end functionality (or, at least giving up up with the defualt array access syntax). If you are going to have negative indexing, there isn't really a better alternative than 1 based indexes; since you can't exactly do arr[-0]
  • ghayes 6y ago
    FWIW, I fully support the notation `arr[-0]` as a solution to this problem.
    • MauranKilom 6y ago
      So then what should this code produce? i = -0 return arr[i]
      • ufo 6y ago
        Actually, I think that might work in Javascript! All the numbers are IEE754 floating point numbers and there are separate values for positive and negative zero.
        • disk0 6y ago
          iirc using numeric literal values there's a coercion step—a console example: let arr = new Array(10); // 1e1 => 10 arr[1e1] = 1; console.log(`arr[10] === 1 => ${arr[10] === 1}`) console.log(`arr[1e1] === 1 => ${arr[1e1] === 1}`) So -0 becomes 0: arr[0] = 2; console.log(`arr[0] === 2 => ${arr[0] === 2}`); console.log(`arr[-0] === 2 => ${arr[-0] === 2}`); arr[-0] = 3; console.log(`arr[0] === 3 => ${arr[0] === 3}`); console.log(`arr[-0] === 3 => ${arr[-0] === 3}`);
      • thaumasiotes 6y ago
        So then what should this code produce? i = -0 return arr[i] That code would (assuming an integer value; the question is interesting without reference to the implementation of JavaScript) return arr[0], the first element. Don't think of arr[-1] as indexing the array with a negative number that might have been a positive number. Think of array access from the front, arr[ ], and array access from the back, arr[- ], as separate operations with separate syntax, each of which can accept only nonnegative numbers. arr[i] is of the first type, so you get the first element counted from the front.
    • ufo 6y ago