# xypic: custom arrow shaft(stem)

I've noted that xy-pic have predefined some dir's. The tail and head (tip) are easy to custom (one can learn by xyrefer.pdf), but I find it hard to implement my own shaft types.

Because the dash stem is drawn evenly with a invisible space. I want to control the space step.

Tried \newdir{}{}, \composite{} but in vain. Furthermore, the following code gives ugly downward arrow:

\documentclass{minimal}
\usepackage[all]{xy}
\begin{document}
{
\def\arr{ \ar@{*{\bullet}*{\cdot}*@{>}} }
\xymatrix{ A \arr[dr]\arr[d]\arr[r] &B \\ C&D }
}
\end{document}


xyrefer.pdf is so fuzzy for beginners. Even the yacc style Syntax-List figures are just for compilers, not for human-reading (I would prefer the Unix-command-syntax-style).

Any help ?

% arara: pdflatex