Tikz out-degree not working properly

Question

Changing the out-degree value in the code below doesn't seem to be working. The figure I get always has an out-degree equal to 0. Any ideas why?

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{arrows, positioning}

\begin{document}

\begin{frame}
\begin{figure}
    \centering
    \begin{tikzpicture}
        [
            state/.style={fill=blue!30, circle, minimum size=0.5cm},
            transition/.style={>=stealth'},
        ]

        \node[state, label={-120:$q_1$}] (q1) {};

        \def\n{4}
        \foreach \q in {2,...,\n} {
            \pgfmathsetmacro\pq{\q-1}                       % previous node index
            \node[state, label={-120:$q_\q$}, right=of q\pq] (q\q) {};  % node
            \draw[transition, ->] (q\pq) to (q\q);                  % transition level 1

            % transition level 2
            \edef\tempa{\q}
            \edef\tempb{2}
            \ifx\tempa\tempb
            \else
                \pgfmathsetmacro\ppq{\q-2};     % 2nd previous node
                \edef\new{q\ppq};

                %%%% THIS OUT-DEGREE doesn't work
                \draw[transition, ->] (q\ppq) to[out=45, in=135] (q\q);                 
            \fi
        }

    \end{tikzpicture}
\end{figure}

\end{frame}

\end{document}

At the moment, the code generates this figure:

However, I expect to get something like this:

Answer 1

The problem is that \pgfmathsetmacro\ppq{\q-2}; set \ppq to 2.0 and (q2.0) is not the same as (q2). To avoid this you can use \pgfmathsetmacro\ppq{int(\q-2)}; or even better \pgfmathtruncatemacro\ppq{\q-2}; (as suggested by @percusse in the comment).

Here is an example of code (not exactly the same as yours):

\documentclass[tikz,border=7mm]{standalone}
\usetikzlibrary{arrows, positioning}

\begin{document}
  \begin{tikzpicture}
    [
      state/.style={fill=blue!30, circle, minimum size=0.5cm},
      transition/.style={>=stealth'},
    ]

    \node[state, label={-120:$q_1$}] (q1) {};

    \def\n{4}
    \foreach[evaluate={\pq=int(\q-1);\ppq=int(\q-2)}] \q in {2,...,\n} {
      \node[state, label={-120:$q_\q$}, right=of q\pq] (q\q) {};  % node
      \draw[transition, ->] (q\pq) to (q\q);                      % transition level 1
      \ifnum\q>2\relax
        \draw[transition, ->] (q\ppq) to[out=45, in=135] (q\q);   % transition level 2
      \fi
    }
  \end{tikzpicture}
\end{document}