how to use “count” feature?

Question

I want to draw something like this.

But I am not able to get x1,x2, ..., x5 labels. What I am getting is as follows:

So, I included count feature. My code is as follows :

\begin{tikzpicture}[thick]
\tikzset{input/.style={}} 
\tikzset{block/.style={rectangle,draw}}


\node [input, name=input] {};
\node [block, right=1cm of input,minimum width=3cm, minimum height=2.5cm] (a) { };
\node [block, right of=a,minimum width=3cm, minimum height=5cm,node distance=5cm] (b) {};


\begin{scope}[->,>=latex]

\draw[->] (input) -- (a);

\foreach \i [count=\xi] in {2,...,-2}{% 
\draw[->] ([yshift=\i * 0.4 cm]a.east) -- ([yshift=\i * 0.8 cm]b.west) node[right]{\footnotesize{$x_{\xi}$}} ;}

\end{scope}
\end{tikzpicture}

But I am getting a compilation error like this:

 Use of \i doesn't match its definition ... node[right]{\footnotesize{$x_{\xi}$}} ;} 

Answer 1

No problem to compile but in your example you need to use the library positioning. I think it's preferable to give us a complete example, to see if a conflict appears between packages. It's interesting also when you get an error like this to give us the version of the packages that you used.

You can find a lot of examples on tex.se with [count=\xi].

  /pgf/foreach/count=⟨macro⟩from⟨value⟩ (no default) 

This key allows ⟨macro⟩ to hold the position in the list of the current item. The optional from ⟨value⟩ statement allows the counting to begin from ⟨value⟩.

By default the first value of \xi is 1, and you can count the number of iterations for -2 to 2 the last value is 5.