1-based indexing doesn’t work well as soon as you have a start offset within a sequence, from which you want to index. Then the first element is startIndex + 0,

1-based indexing doesn’t work well as soon as you have a start offset within a sequence, from which you want to index. Then the first element is startIndex + 0, not startIndex + 1. 0-based indexing generalizes better in that way.