Reliably trapping end of paragraph / return to vertical mode
David Carlisle
d.p.carlisle at gmail.com
Wed Oct 2 22:17:52 CEST 2019
On Wed, 2 Oct 2019 at 21:14, William F Hammond via texhax <texhax at tug.org>
wrote:
> "Taylor, P" <P.Taylor at rhul.ac.uk> writes in part:
>
> > ... Although Knuth provides \everypar, which can be
> > reliably used to trap entry to a paragraph, there does not
> > appear (to me, at least) to be any 100% reliable method of
> > trapping exit therefrom, and of course once the next
> > paragraph has been entered, the previous (and desired)
> > value of \prevgraf has been lost. ...
>
> I'm going to present what is going through my mind as a list
> of questions. I am not in urgent need of answers for
> myself.
>
> 1. Does \par begin or end a paragraph?
>
end (the \par primitive), the \par token can do anything it is defined to do
> 2. Does a blank line begin or end a paragraph?
>
with normal catcode and endlinechar settings it generates a \par token
then does whatever \par is defined to be
>
> 3. Is there any difference at all between \par
> and a blank line?
>
not with normal settings (verbatim etc changes this)
> 4. For the previous questions is there any difference
> between plainTeX and LaTeX?
>
>
not really except that latex redefines the \par token not to be the \par
primitive in a lot more places than plain does,
> -- Bill
>
>
>
David
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