Tikz offers a library for drawing finite state automata (FSA) for embedding in LaTeX. As I mostly use simple FSAs and for making the corresponding Tikz code more expressive, I created two new commands:
- newState
Each state has an internal name which may be referred to when drawing edges and a visible label. In contrast toother graph drawing tools such as GraphViz we need to provide positioning information for each node (above of/below of/right of/left of). Each state may bear additional properties such as whether it is an accepting state or an initial state. - newTransition
A transition connects a source state with a target state, given that some condition is fulfilled guard. An edge may be drawn as a straight line (default) or as an arc (bend left/bend right). For loops you need to use loop above/loop below etc.
Example FSA
Finite State Automaton drawn with Tikz
The following example code defines an FSA which accepts words conforming to the regular expression b(an)+e:
documentclass{scrartcl}
usepackage{tikz}
usetikzlibrary{arrows,automata}
% newState{}{}{}{}
%
% #1: internal name,
% #2: (visible) label,
% #3: node properties (e.g. accepting, initial)
% #4: relative position (e.g. right of=/left of=/above of=/below of=)
newcommand{newState}[4]{node[state,#3](#1)[#4]{#2};}
% newTransition{}{}{}{}
% #1: source state (internal name),
% #2: target state (internal name)
% #3: guard/edge label
% #4: edge direction (loop below/above, bend right/left)
newcommand{newTransition}[4]{path[->] (#1) edge [#4] node {#3} (#2); }
begin{document}
begin{figure}
begin{tikzpicture}[
% Default arrow tip
->,>=stealth',shorten >=1pt,auto,
% Default node distance
node distance=2cm,
% Edge stroke thickness: semithick, thick, thin
semithick
]
newState{S}{$S$}{initial}{}
newState{q1}{$q_1$}{right of=S}{}
newState{q2}{$q_2$}{below of=q1}{}
newState{q3}{$q_3$}{right of=q1}{accepting}
newTransition{S}{q1}{b}{}
newTransition{q1}{q2}{a}{bend left}
newTransition{q2}{q1}{n}{bend left}
newTransition{q1}{q3}{e}{}
end{tikzpicture}
caption{Finite State Automaton, accepting the pattern emph{b(an)+e}}
end{figure}
end{document}
GraphViz as an Alternative
Another candidate for drawing graphs is GraphViz, which I indeed tested first. GraphViz has some important drawbacks:
- The subscript tag <SUB> and some others do not work for GraphViz before the version of October 14, 2011, and even then, only for PNG and SVG rendering.[1]
- The font used for rendering by GraphViz is not synchronized with the font in the final LaTeX document which may be annoying.