2

I sometimes have to write diagrams where I write a map as composition of finitely many others. I then want to typeset things like A_1->A_2->...->A_n. Right now, I use the following code to do that

\documentclass{article}
\usepackage[utf8]{inputenc}                                    
\usepackage[T1]{fontenc}
\usepackage[all,cmtip]{xy}
\begin{document}
\begin{displaymath}
\xymatrix{
A_1\ar@{->}[r]&A_2\ar@{->}[r]&\cdots \ar@{->}[r] & A_n
}
\end{displaymath}
\end{document}

This is working and looks okay. But if I have a larger diagram like

\documentclass{article}
\usepackage[utf8]{inputenc}                                    
\usepackage[T1]{fontenc}
\usepackage[all,cmtip]{xy}
\begin{document}
\begin{displaymath}
\xymatrix{
&&&\txt{Something larger}\\
A_1\ar@{->}[r]&A_2\ar@{->}[r]&\cdots \ar@{->}[r] & A_n
}
\end{displaymath}
\end{document}

the arrows start to have different lengths. This is still okay (although not too nice looking), but when it comes to diagonal arrows, the arrows are no longer in line and it finally looks very ugly:

\documentclass{article}
\usepackage[utf8]{inputenc}                                    
\usepackage[T1]{fontenc}
\usepackage[all,cmtip]{xy}
\begin{document}
\begin{displaymath}
\xymatrix{
\ar@{->}[dr]&&&\\
&\ddots\ar@{->}[dr] &\txt{long sample text}&\\
&&&
}
\end{displaymath}
\end{document}

I therefore thought that the best solution would be an arrow that looks like "->...->" which does not seem to exist. Also since I am more a user than a developer to TeX, I am unable to build this on my own. Any help is appreciated.

1

I now have a more or less satisfying answer:

\documentclass{article}
\usepackage[utf8]{inputenc}                                    
\usepackage[T1]{fontenc}
\usepackage[all,cmtip]{xy}
 \newdir{d>}{!/-11.0pt/@{ }*:(0,0)@{>}}
\begin{document}
\begin{displaymath}
\xymatrix{
A\ar[r] |-{\object@{d>}}|{\object@{ }}|-{\;\dots\;}  & B}
\end{displaymath}
\end{document}

This isn't a perfect solution and I would still be happy to see anyone come up with something better. But this at least works better than the default.

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