Say that I want to highlight a region expressed in terms of two coordinates of the form
(line, column), e.g.
C1 = (l1, c1) to
C2 = (l2, c2).
:h matchaddpos() but it seems that you can only specify entire lines or single characters to highlight, or you can express a range through starting position + length, which would lead to not very readable solutions, although the latest could be interesting as it would require the definition of a distance in the metric space built on the buffer’s coordinates set.
:h matchadd() requires a pattern but I am not sure how should I specify patterns for ranges expressed in terms of coordinates of the form