# Bending arrow in XY-Pic diagram

In the diagram with bending arrow given by the LaTeX file below, the arrow has a misdirected head.

How can I correct it?

\documentclass[a4paper,11pt]{amsart}
\usepackage[all]{xy}
\begin{document}
$\xymatrix@1@R=7pt@C=10pt{ & 0 \ar@{-}[rd] &&&& 1\ar@{-}[ld] \\ && a\ar@{-}[r] & \cdots \ar@{-}[r] & b \\ &2\ar@{-}[ru] &&&& 3\ar@{-}[lu] \ar@{-->} d[dl] [lllll] [uu] \\ &&&& }$
\end{document}

• I heartily wish that bending arrows were more clearly explained in the manual of Xy-pic. – egreg Jun 5 '15 at 20:11

One possible solution is in the following code. Essentially I just added one more relative positioning parameter to get the arrowhead to turn the correct direction. Also, I changed the variant of the arrow head \ar@{--2>} to make the arrow more distinct.

\documentclass[a4paper,11pt]{amsart}
\usepackage[all]{xy}
\begin{document}
$\xymatrix@1@R=7pt@C=10pt{ & 0 \ar@{-}[rd] &&&& 1\ar@{-}[ld] \\ && a\ar@{-}[r] & \cdots \ar@{-}[r] & b \\ &2\ar@{-}[ru] &&&& 3\ar@{-}[lu] \ar@{--2>} d[dl] [lllll] [uu] [uullll] \\ &&&& }$
\end{document}


• How can one put a picture in one's question or answer? – Mikhail Borovoi Jun 6 '15 at 6:28
• @MikhailBorovoi: You're welcome! To add a picture to the answer box you can press the little box that looks like a landscape (at the top of the editor) and then either upload an image from your computer, or through a url, or you can do Ctrl-G on Windows. – cptnjtk Jun 6 '15 at 6:34
• @cptnjtk, not only on Windows. I use Linux and ctrl+g works. – Sigur Jun 6 '15 at 12:20

If you want to get the whole arrow dashed, you will have to switch to :

% arara: pdflatex

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}
$\begin{tikzcd}[every arrow/.append style={dash}] 0 \arrow{dr} & &[.8cm] & 1 \\ & a \arrow{r}[description]{\ldots} & b \arrow{ur}\arrow{dr} & \\ 2 \arrow{ur} & & & 3 \arrow[->, dashed, rounded corners, to path={ -- ([yshift=-2ex]\tikztostart.south) -| ([xshift=-2ex]\tikztotarget.west) -- (\tikztotarget)}]{uulll} \end{tikzcd}$
\end{document}


• Excellent! I will certainly switch to {tikz-cd}! Unfortunately, I cannot accept two answers.... – Mikhail Borovoi Jun 9 '15 at 14:19
• @MikhailBorovoi Glad to hear that. You do not have to accept both. The other one answers your question. I am just giving another approach. It is absolutely worth to have a look into the tikz-cd manual. – LaRiFaRi Jun 9 '15 at 14:21