tkz-euclide and Xy-pic conflict over Babel shorthands

Question

It is well known that certain Babel shorthands conflict with some Xy-pic commands and this can be solved by disabling those shorthands. I was using Xy-pic and Babel french with shorthands=off in the options list. That worked.

However, I now must combine a number of files, some written long ago using Xy-pic and some written using tkz-euclide. The tkz-euclide will not work with shorthands=off.

The file below certainly will not compile for me, but it does work when I comment out the babel line, so I believe the shorthands problem is the reason why it does not compile:

\documentclass{amsart}
\usepackage{xy}
\input xy
\xyoption{all}
%\usepackage[french]{babel}
\begin{document}
\xy   ,(100,0);(100,0)
        ,(97,6)="A"
        ,"A"+(-4.5,-1);"A"+(4.5,-1)  *\crv{"A"+(-3.4,-6)&"A"+(3.4,-6)}
\endxy
\end{document}

It produces an error messge

! Xy-pic error: <pos> "A" not defined.
\xyerror@ ...#2}\fi \errmessage {Xy-pic error: #1}

So I tried using \shorthandoff{"} in several places, and I tried "A and "A" and A" but got messages saying they are not shorthands. I tried putting just \shorthandoff in front of the first offending XY-pic in the file and that had no effect.

I suspect the simplest solution would be to identify which shorthands the Xy-pics conflict with and just disable those. But I cannot identify them. I do not know what all the babel french shorthands are. The fullest description I have found so far is the Babel language definition file for French frenchb.dtx v3.3d, 2017/10/19

at http://daniel.flipo.free.fr/frenchb/frenchb.pdf

But it does not list " as a babel french shorthand.

Of course it is possible that tkz-euclide actually requires some specific shorthand that conflicts with some specific Xy-pic command I need to use. But I hope there is some simple solution.

Answer 1

As Ulrike Fischer points out ; is a shorthand in French. Indeed the babel documentation lists the following symbols as French shorthands:

:;?!

These are used to implement French spacing conventions for these punctuation symbols.

You can turn these off explicitly with \shorthandsoff. Enclose this in group to limit its scope.

\documentclass{amsart}

\usepackage[main=french]{babel}
\usepackage[all]{xy}

\begin{document}

{\shorthandoff{:;?!}%
  \xy   ,(100,0);(100,0)
        ,(97,6)="A"
        ,"A"+(-4.5,-1);"A"+(4.5,-1)  *\crv{"A"+(-3.4,-6)&"A"+(3.4,-6)}
\endxy}

\end{document}

Answer 2

Using proper LaTeX syntax allows doing the \shorthandoff operation automatic inside xy.

For TikZ based packages, remember to \usetikzlibrary{babel}.

\documentclass{amsart}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}

\usepackage[all]{xy}
\usepackage{etoolbox}

\AtBeginEnvironment{xy}{\shorthandoff{?!:;}}

\begin{document}

\begin{xy}
   ,(100,0);(100,0)
   ,(97,6)="A"
   ,"A"+(-4.5,-1);"A"+(4.5,-1)  *\crv{"A"+(-3.4,-6)&"A"+(3.4,-6)}
\end{xy}

\end{document}