How to decrease the counter in tikz foreach loop

Question

I have the following code:

\documentclass[11pt]{article}
\usepackage[a4paper]{geometry}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{tikz}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[node distance = 0.5cm, auto]
\node (0) {Block 0};
\node (1) [below= of 0.south] {Block 1};
\node (2) [below= of 1.south] {Block 2};
\end{tikzpicture}
\end{document}

It prints this:

enter image description here

I tried to do the same with pgf loop, but don't know how to decrease the counter:

\foreach \x in {0,...,2}
{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      %\prev=\x - 1 <- ???
      \node (\x) [below= of \prev.south] {Block \x};
  \fi
}

The .south is not needed, see Package PGF Math Error: Unknown operator — Qrrbrbirlbel, Apr 23 '13 at 21:42
@Qrrbrbirlbel Plz, mention, that I included positioning library at the top snippet. So, it's ok. — user4035, Apr 23 '13 at 21:48
As the linked question shows, the positioning library actually makes =of possible. What I meant was, that below implicitly sets the .south anchor of the “of” node. It doesn’t hurt either. — Qrrbrbirlbel, Apr 23 '13 at 21:53
You might prefer naming nodes with some other pattern because right now it's hanging in the balance waiting TikZ to confuse it with a regular number :) — percusse, Apr 23 '13 at 21:59
In this simple case we can also use \foreach \x [remember=\x as \eval] in … and don't need to calculate anything. — Qrrbrbirlbel, Apr 26 '13 at 17:16

score 11 · Accepted Answer · answered Apr 23 '13 at 21:35

11

You can use math :)

\foreach \x in {0,...,2}{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      \pgfmathparse{int(\x-1)}
      \node (\x) [below= of \pgfmathresult.south] {Block \x};
  \fi
}

answered Apr 23 '13 at 21:35

percusse

157,807

3

Must... resist... posting... this... link... :) – Paulo Cereda Oct 21 '13 at 13:42

Qrrbrbirlbel · Answer 2 · 2013-10-21T13:08:02.353

Besides using \pgfmathparse{int(…)} you can also use \pgfmathtruncatemacro or:

eTeX’s \numexpr,
\foreach’s evaluate (again with int),
\foreach’s remember,
\foreach’s count starting from -1 (i.e. first \x minus one)
(recommended) the chains library with start chain=<chain name> going below.

Code

\documentclass[tikz]{standalone}
\usetikzlibrary{positioning,chains}
\tikzset{node distance=.5cm}
\begin{document}
\begin{tikzpicture}
\foreach \x in {0,...,2}{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      \node (\x) [below=of \number\numexpr\x-1\relax] {Block \x};
  \fi
}
\end{tikzpicture}

\begin{tikzpicture}
\foreach \x[evaluate=\x as \eval using int(\x-1)] in {0,...,2}{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      \node (\x) [below=of \eval] {Block \x};
  \fi
}
\end{tikzpicture}

\begin{tikzpicture}
\foreach \x[remember=\x as \eval] in {0,...,2}{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      \node (\x) [below=of \eval] {Block \x};
  \fi
}
\end{tikzpicture}

\begin{tikzpicture}
\foreach \x[count=\eval from -1] in {0,...,2}{
  \ifnum\x=0\relax
      \node (\x) {Block \x};
  \else
      \node (\x) [below=of \eval] {Block \x};
  \fi
}
\end{tikzpicture}

\begin{tikzpicture}[start chain=going below]
\foreach \x in {0,...,2}
  \node[on chain] (\x) {Block \x};
\end{tikzpicture}
\end{document}

Output (all solutions)

enter image description here

How to decrease the counter in tikz foreach loop

2 Answers2

Code

Output (all solutions)

Linked

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