# Harpoons in TikZ

Can I have any harpoons in TikZ?

I refer to my previous question on harpoons: "How to draw protocol interaction" using amsmath.
The closest thing I have found is this code:

\begin{tikzpicture}[decoration={bent,aspect=.3}]
\node[circle,draw] (A) at (.5,.5) {A};
\node[circle,draw] (B) at (3,1.5) {B};
\draw[->,decorate] (A) -- (B);
\draw[->,decorate] (B) -- (A);
\end{tikzpicture}

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There are so called partial arrow tips in TikZ. Use for instance left to, right to, left hook or right hook. They are desribed in section 23.7 of the pfg 2.10 manual (22.6 in the pgf 2.0 manual).

Inserting this into your example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}
\node[circle,draw] (A) at (.5,.5) {A};
\node[circle,draw] (B) at (3,1.5) {B};
\draw[-left to] (A.north east) -- (B.west);
\draw[-left to] (B) -- (A);
\end{tikzpicture}
\end{document}


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I saw that manual. I need two arrows over each other to show protocol interaction. Can you put two arrow connected to two nodes atop of each other in a way that implies simultaneous exchange of messages? –  Yasser Sobhdel Dec 11 '10 at 15:31
@Yasser: I've added an example. –  Stefan Kottwitz Dec 11 '10 at 15:50
Thanks. That's it. –  Yasser Sobhdel Dec 11 '10 at 16:48