[texhax] What can I about \\ added at par ends?

[Paul Isambert]

Selon Michael Barr <barr at math.mcgill.ca>:

> I have an ms that is to be published in the online journal I do the tex
> editing for.  For reasons I don't want to go into, I cannot ask him to
> revise it; it was put into tex by a grad student, not by the author.  The
> grad student ended every paragraph with \\ followed by a blank line.  You
> can see the effect from this simple file:
>
> \documentclass{article}
> \begin{document}
> This is a test of what \\
>
> does to add to parskip\\
>
> and again
>
> And here it is without the\\
>
> \end{document}
>
> There are 1063 instances of \\ in the file and probably several dozen are
> actually appropriate, maybe a 100.  (This ms compiles to 170 pages.)  I am
> not about to go through it and take out the ones that shouldn't be there.
> One thing I tried was \parskip -5pt.  This helped but are a few instances
> where the student "forgot" to add the \\.  So is there any way to nullify
> the effect of \\ when it is followed by a blank line (or, presumably, a
> \par) but still has the correct effect otherwise?

As Bob recommended, a good text editor could easily do the job; if
your editor doesn't do regex search/replace, you might consider
switching to another one :), or try the following (probably not
extremely robust) snippet:

    \bgroup
    \def\dospace#1{%
      \global\let\spacechar=
      }
    \dospace{} %
    \egroup

    \def\checkpar{%
      \futurelet\next\docheckpar
      }

    \def\docheckpar{%
      \ifx\next\spacechar
        \expandafter\recheckpar
      \else
        \unless\ifx\next\par
          \expandafter\expandafter\expandafter\doublebackslash
        \fi
      \fi
      }

    \def\recheckpar{%
      \afterassignment\checkpar\let\next=
      }

    \let\doublebackslash=\\
    \let\\=\checkpar

Best,
Paul