Selon Nicolas Pillot <nicolas(_dot_)pillot(_at_)polymtl(_dot_)ca>:
I have a problem, as you can guess. I am struggling to find the element
that is just before, and the element just after the current one.
Well, i feel stupid now. I just spent time posting this question,
and i found the answer by refining my search on google.
Here is how it could be done :
n-th previous element is preceding-sibling::*[n]
so element just before current is preceding-sibling::*[1]
n-th next element is following-sibling::*[n]
so element just after current is following-sibling::*[1]
Sorry for the inconvenience of these two posts.
Nicolas