# Is it possible to use marking of decoration with edge?

The initial code is

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations}
\usetikzlibrary{decorations.markings}
\begin{document}

\pgfkeys{
/pgf/decoration/.cd,
}

\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (4,2);

\draw [
decoration={
curveto,
pre=moveto, pre fraction=0,
post=moveto, post fraction=0.3}, decorate, red, ultra thick] (A) to[out=0,in=-90](B);

\draw [decoration={curveto,
pre=moveto, pre fraction=0.7,
post=moveto, post fraction=0},%
decorate, blue, ultra thick,dotted] (A) to [out=0,in=-90](B);

\path [
decoration={
markings, mark=at position .7  with {\arrow[red,line width=2pt]{>}}},
decorate  ] (A) to[out=0,in=-90](B);
\end{tikzpicture}

\end{document}


There is a problem if I want to replace to by edge . In some cases, the replacement is useful.

Is it possible to use making with edge ? and how ?

I think that the problem comes from that the edge operation works like a to operation that is added after the main path has been drawn. I get often the error that marking does not work on an empty path !

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Finally I found the answer here: texblog.net in the article: Decorate a TikZ path. (Author: Stefan Kottwitz thanks!). I do not know why I did not think earlier. There are many questions related to the use of edge that can be resolved like this, example: Strange arrow mark with TikZ edge and anchors.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations}
\usetikzlibrary{decorations.markings}
\begin{document}

\begin{tikzpicture}
\tikzset{every loop/.style={min distance=20mm,in=0,out=60,looseness=10}}

\draw (0,0) node[circle,draw]{A} edge[red,loop]  ();
\path[decoration={
markings, mark=at position .7  with {\arrow[blue,line width=1pt]{>}}}] (0,0) node[circle]{A} edge[decorate,loop]  ();
\end{tikzpicture}

\end{document}


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