How to change the arrows tips for the whole document?

Question

After I asked this question: What is "\SelectTips{a}{b}" (and how to increase the head of an arrow's head?)
I'd like to know one more thing: I want to change it (the arrow tips) for the whole document, i.e. - right now, if I want to change the arrow tip I need to put the command \SelectTips{eu}{} (for example) at math-mode for every formula or graph that I make (especially at xy-pic).

Is there a way to put it at the Preamble that it will influence all the document? (all of the arrows tips at math-mode).

Thank you!

Answer 1

You can put \everyxy={\SelectTips{eu}{}} in your preamble:

\documentclass{article}
\usepackage[all]{xy}
\everyxy={\SelectTips{eu}{}}
\begin{document}
First:
\[\xymatrix{
    A_1\ar[r]\ar[d] & A_2\ar[d]\\
    A_3\ar[r] & A_4
}\]
Second:
\[\xymatrix{
    B_1\ar[r]\ar[d] & B_2\ar[d]\\
    B_3\ar[r] & B_4
}\]
\end{document}