How to generate many anchors inside \pgfdeclareshape?

Question

In defining a new shape with \pgfdeclareshape, I have problems to add many anchors with the \foreach statement. Each anchor is defined with three arguments. In the example, the argument #1 is OK but the program complains with #2 and #3. How can I generate so many anchors with different keys with \foreach?

\documentclass[a4paper,landscape]{article}
\usepackage{tikz}
\usetikzlibrary{calc,arrows}
\usepackage{amsmath}
\usepackage[left=1cm,right=1cm]{geometry}
\pagestyle{empty}

\begin{document}
\makeatletter
% Define shapes
\pgfdeclareshape{PE}{
  % Inherit from rectangle
  \inheritsavedanchors[from=rectangle]
  \inheritanchor[from=rectangle]{center}
  \inheritanchorborder[from=rectangle]

  % In the following I want to make many anchors with some loop. For example,
  %\foreach \x/\Y/\z in {een/1/.7,ee/1/0,ees/1/-1}
  %{\anchor{\x}{
  %  \pgf@process{\northeast}%
  %  \pgf@x=\y\pgf@x%
  %  \pgf@y=\z\pgf@y%
  %}}
  %However, while #1 is replaced but #2 and #2 are not. 
  %How can I use \foreach or TeX loop?        

  \anchor{een}{
    \pgf@process{\northeast}%
    \pgf@x=1\pgf@x%
    \pgf@y=.7\pgf@y%
  }
  \anchor{ee}{
    \pgf@process{\northeast}%
    \pgf@x=1\pgf@x%
    \pgf@y=0\pgf@y%
  }
  \anchor{ees}{
    \pgf@process{\northeast}%
    \pgf@x=1\pgf@x%
    \pgf@y=-.7\pgf@y%
  }
    \anchor{se}{
    \pgf@process{\northeast}%
    \pgf@x=1\pgf@x%
    \pgf@y=-1\pgf@y%
  }

  % Draw the rectangle box and the port labels
  \backgroundpath{
    % Rectangle box
    \pgfpathrectanglecorners{\southwest}{\northeast}
  %Add labels
  %The following code doesn't work.
  %\foreach \x/\y in {een,ee,ees}
  %  {
  %  \pgf@anchor@PE@\x
  %  \pgftext[at={\pgfpoint{\pgf@x}{\pgf@y}},x=-\pgfshapeinnerxsep,y=0]{\raisebox{-.75ex}{\y}}
  % }
  %\foreach \x/\y in {anchor@PE@een/een,\pgf@anchor@PE@ee/ee,\pgf@anchor@PE@ees/ees}
  %{
  %  \x
  %  \pgftext[at={\pgfpoint{\pgf@x}{\pgf@y}},x=-\pgfshapeinnerxsep,y=0]{\raisebox{-.75ex}{\y}}
  %}
}
\makeatother

\begin{tikzpicture}[>=stealth']
  \tikzset{PE/port labels/.style={font=\sffamily\scriptsize}}
  \tikzset{every PE node/.style={draw=blue,minimum width=2cm,minimum
    height=3cm,very thick,inner sep=1mm,outer sep=0pt,cap=round}}
  % Place PEs
  \foreach \m in {0,...,3}
    \node [shape=PE] (PE\m) at ($ 4*(\m,0)$) {};
\end{tikzpicture}
\end{document}

Answer 1

Expanding in foreach loops is always problematic so you need to make sure that macros are expanded properly (or some of them are nor expanded while the variables are expanded)

\documentclass[border=2mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,arrows}

\makeatletter

\pgfdeclareshape{PE}{

  \inheritsavedanchors[from=rectangle]
  \inheritanchor[from=rectangle]{center}
  \inheritanchorborder[from=rectangle]

  \foreach \x/\z in {een/.7,ee/0,ees/-1}
  {
    \xdef\doanchor{
      \noexpand\anchor{\x}{
      \noexpand\northeast
      \noexpand\pgf@y=\z\noexpand\pgf@y%
      }
    }\doanchor
  }
  \backgroundpath{
    % Rectangle box
    \pgfpathrectanglecorners{\southwest}{\northeast}
  }
}
\makeatother

\begin{document}

\begin{tikzpicture}[>=stealth']
  \tikzset{PE/port labels/.style={font=\sffamily\scriptsize}}
  \tikzset{every PE node/.style={draw=blue,minimum width=2cm,minimum
    height=3cm,very thick,inner sep=1mm,outer sep=0pt,cap=round}}
  % Place PEs
  \foreach \m in {0,...,2}{    \node [shape=PE] (PE\m) at ($ 4*(\m,0.25*\m)$) {};}
    \draw (PE0.een) to[bend right] (PE1.ee) to[bend right] (PE2.ees);
    %\draw (PE0.ees) -|++(3cm,-2cm) -| (PE1.ees);
    \node at (PE2.een)  {a};
    \node at (PE2.ee)   {b};
    \node at (PE2.ees)  {c};
\end{tikzpicture}
\end{document}