The exercise is to reproduce the two possible typings of ```
(three leftquotes). Immediately beforehand there is an explanation of how to do the same thing with three rightquotes, which I will rewrite in my own words to check I really understand it:
If you type
'''
, then TeX assumes that this is a double\rq
followed by a single\rq
, and spaces appropriately. If you group them this way, you have:'''
vs.''{'}
, which I expect to look identical (they do). But if you want a single\rq
followed by a double\rq
, then grouping does not work:'{''}
because the space is too small. So you have to manually insert the\thinspace
: to get'\thinspace''
For the exercise, I figured that three leftquotes in a row ```
would be parsed as "double \lq
followed by single \lq
", and that therefore the spacing would agree with ``\thinspace'
, but it doesn't. I know from elsewhere that two adjacent backticks get turned into a ligature. I assumed that the spacing between this ligature and the surrounding text was determined dynamically (somehow), but if the ``
ligature actually has some space hard-coded (i.e. that it really becomes \thinspace``
) then I think I understand (in particular, Don's remarks about spacing in the previous paragraph also seem to make sense). Is this correct?