Drawing automata The drawing of graphs described here uses graphviz , a software for drawing graphs developed at AT \& &amp; & T Labs, that can be obtained at https://www.graphviz.org/.
Installing some external programs In order to create the drawings you should have https://www.graphviz.org/ installed and to view them you should have installed some pdf viewer.
Functions to draw automata This function draws automaton A. The arguments state_names, L and file are optional.

An automaton with n states will be drawn with numbers 1 to n written inside the corresponding graph node. The argument state_names is a list of n strings which will be the new text written inside the corresponding graph node.

The argument L is a list of lists of integers, each of which specifies a set of states to be drawn in a different color.
gap> x:=Automaton("det",3,2,[ [ 2, 3, 0 ], [ 0, 1, 2 ] ],[ 1 ],[ 1, 2, 3 ]);; gap> DrawAutomaton(x); gap> DrawAutomaton(x,["st 1", "2", "C"]); gap> DrawAutomaton(x,["st 1", "2", "C"],[[2],[1,3]]);
The output of the three previous DrawAutomaton commands would be the following diagrams, respectively.

\begin{figure}[htbp] \begin{center} \leavevmode \includegraphics[bb=0 0 74 250]{aut2.jpg} \end{center} \label{fig:aut2} \end{figure} <br><center><img src="aut2.jpg"></center><br>

\begin{figure}[htbp] \begin{center} \leavevmode \includegraphics[bb=0 0 100 250]{aut2_1.jpg} \end{center} \label{fig:aut2_1} \end{figure} <br><center><img src="aut2_1.jpg"></center><br>

\begin{figure}[htbp] \begin{center} \leavevmode \includegraphics[bb=0 0 100 250]{aut2_2.jpg} \end{center} \label{fig:aut2_2} \end{figure} <br><center><img src="aut2_2.jpg"></center><br> This function computes the dot code that can be used to display an automaton. This can be done by using the function (if the system is properly configured) or by the user in some independent way. The arguments and options are the same than those of .
gap> DotStringForDrawingAutomaton(x); "digraph Automaton{\n\"1\" -> \"2\" [label=\"a\",color=red];\n\"2\" -> \"3\" \ [label=\"a\",color=red];\n\"2\" -> \"1\" [label=\"b\",color=blue];\n\"3\" -> \ \"2\" [label=\"b\",color=blue];\n\"1\" [shape=triangle,peripheries=2, style=fi\ lled, fillcolor=white];\n\"2\" [shape=doublecircle, style=filled, fillcolor=wh\ ite];\n\"3\" [shape=doublecircle, style=filled, fillcolor=white];\n}\n"
By using Print (or PrinTo, if one wants to print to a file) the string is displayed as follows:
gap> Print(last); digraph Automaton{ "1" -> "2" [label="a",color=red]; "2" -> "3" [label="a",color=red]; "2" -> "1" [label="b",color=blue]; "3" -> "2" [label="b",color=blue]; "1" [shape=triangle,peripheries=2, style=filled, fillcolor=white]; "2" [shape=doublecircle, style=filled, fillcolor=white]; "3" [shape=doublecircle, style=filled, fillcolor=white]; }
The dot code produced for the remaining pictures:
gap> Print(DotStringForDrawingAutomaton(x,["st 1", "2", "C"])); digraph Automaton{ "st 1" -> "2" [label="a",color=red]; "2" -> "C" [label="a",color=red]; "2" -> "st 1" [label="b",color=blue]; "C" -> "2" [label="b",color=blue]; "st 1" [shape=triangle,peripheries=2, style=filled, fillcolor=white]; "2" [shape=doublecircle, style=filled, fillcolor=white]; "C" [shape=doublecircle, style=filled, fillcolor=white]; } gap> Print(DotStringForDrawingAutomaton(x,["st 1", "2", "C"],[[2],[1,3]])); digraph Automaton{ "st 1" -> "2" [label="a",color=red]; "2" -> "C" [label="a",color=red]; "2" -> "st 1" [label="b",color=blue]; "C" -> "2" [label="b",color=blue]; "st 1" [shape=triangle,peripheries=2, style=filled, fillcolor=burlywood]; "2" [shape=doublecircle, style=filled, fillcolor=brown]; "C" [shape=doublecircle, style=filled, fillcolor=burlywood]; }
This function tests if automaton A is a subautomaton of B in which case draws B highlighting the edges not in A by drawing them in a dotted style, while the others are drawn in a plain style.
gap> A := Automaton("nondet",5,"abc",[ [ [ 2, 3 ], [ 5 ], [ 1, 4, 5 ], [ 1, 5 ], [ 3, 4 ] ], [ [ 1, 4, 5 ], [ ], [ 1 ], [ 1, 3, 5 ], [ 1, 2, 5 ] ], [ [ ], [ 2, 4, 5 ], [ 1, 3, 5 ], [ ], [ 2, 3, 4 ] ] ],[ ],[ 2, 3, 4 ]);; gap> B := Automaton("nondet",5,"abc",[ [ [ 2, 3 ], [ 5 ], [ 1, 4, 5 ], [ 1, 5 ], [ 3, 4 ] ], [ [ 1, 4, 5 ], [ ], [ 1 ], [ 1, 3, 5 ], [ 1, 2, 5 ] ], [ [ 1, 4, 5 ], [ 2, 4, 5 ], [ 1, 3, 5 ], [ 2, 3, 4, 5 ], [ 2, 3, 4 ] ] ],[ 3, 4, 5 ],[ 2, 3, 4 ]);; gap> DrawSubAutomaton(A,B);
The output is as follows, in case the configuration of your computer permits. Otherwise, you may be interested in the dot code, as pshown below.

\begin{center} \includegraphics[width=0.5\textwidth]{subaut.jpg} \end{center} <br><center><img src="subaut.jpg"></center><br>

This function computes the dot code that can be used to draw automata A, with the subsutomaton B emphasized. It is silently used by the function (if the system is properly configured) or can be used by the user in some independent way.
gap> DotStringForDrawingSubAutomaton(A,B); "digraph Automaton {\n1 -> 2 [label=\"a\",color=red];\n1 -> 3 [label=\"a\",co\ lor=red];\n1 -> 1 [label=\"b\",color=blue];\n1 -> 4 [label=\"b\",color=blue];\ \n1 -> 5 [label=\"b\",color=blue];\n1 -> 1 [label=\"c\",color=green,style = do\ tted];\n1 -> 4 [label=\"c\",color=green,style = dotted];\n1 -> 5 [label=\"c\",\ color=green,style = dotted];\n2 -> 5 [label=\"a\",color=red];\n2 -> 2 [label=\ \"c\",color=green];\n2 -> 4 [label=\"c\",color=green];\n2 -> 5 [label=\"c\",co\ lor=green];\n3 -> 1 [label=\"a\",color=red];\n3 -> 4 [label=\"a\",color=red];\ \n3 -> 5 [label=\"a\",color=red];\n3 -> 1 [label=\"b\",color=blue];\n3 -> 1 [l\ abel=\"c\",color=green];\n3 -> 3 [label=\"c\",color=green];\n3 -> 5 [label=\"c\ \",color=green];\n4 -> 1 [label=\"a\",color=red];\n4 -> 5 [label=\"a\",color=r\ ed];\n4 -> 1 [label=\"b\",color=blue];\n4 -> 3 [label=\"b\",color=blue];\n4 ->\ 5 [label=\"b\",color=blue];\n4 -> 2 [label=\"c\",color=green,style = dotted];\ \n4 -> 3 [label=\"c\",color=green,style = dotted];\n4 -> 4 [label=\"c\",color=\ green,style = dotted];\n4 -> 5 [label=\"c\",color=green,style = dotted];\n5 ->\ 3 [label=\"a\",color=red];\n5 -> 4 [label=\"a\",color=red];\n5 -> 1 [label=\"\ b\",color=blue];\n5 -> 2 [label=\"b\",color=blue];\n5 -> 5 [label=\"b\",color=\ blue];\n5 -> 2 [label=\"c\",color=green];\n5 -> 3 [label=\"c\",color=green];\n\ 5 -> 4 [label=\"c\",color=green];\n3 [shape=triangle,color=gray];\n4 [shape=tr\ iangle,color=gray];\n5 [shape=triangle,color=gray];\n2 [shape=doublecircle];\n\ 3 [shape=doublecircle];\n4 [shape=doublecircle];\n1 [shape=circle];\n}\n"
By using Print (or PrinTo, if one wants to print to a file) the string is displayed as follows:
gap> Print(last); digraph Automaton { 1 -> 2 [label="a",color=red]; 1 -> 3 [label="a",color=red]; 1 -> 1 [label="b",color=blue]; 1 -> 4 [label="b",color=blue]; 1 -> 5 [label="b",color=blue]; 1 -> 1 [label="c",color=green,style = dotted]; 1 -> 4 [label="c",color=green,style = dotted]; 1 -> 5 [label="c",color=green,style = dotted]; 2 -> 5 [label="a",color=red]; 2 -> 2 [label="c",color=green]; 2 -> 4 [label="c",color=green]; 2 -> 5 [label="c",color=green]; 3 -> 1 [label="a",color=red]; 3 -> 4 [label="a",color=red]; 3 -> 5 [label="a",color=red]; 3 -> 1 [label="b",color=blue]; 3 -> 1 [label="c",color=green]; 3 -> 3 [label="c",color=green]; 3 -> 5 [label="c",color=green]; 4 -> 1 [label="a",color=red]; 4 -> 5 [label="a",color=red]; 4 -> 1 [label="b",color=blue]; 4 -> 3 [label="b",color=blue]; 4 -> 5 [label="b",color=blue]; 4 -> 2 [label="c",color=green,style = dotted]; 4 -> 3 [label="c",color=green,style = dotted]; 4 -> 4 [label="c",color=green,style = dotted]; 4 -> 5 [label="c",color=green,style = dotted]; 5 -> 3 [label="a",color=red]; 5 -> 4 [label="a",color=red]; 5 -> 1 [label="b",color=blue]; 5 -> 2 [label="b",color=blue]; 5 -> 5 [label="b",color=blue]; 5 -> 2 [label="c",color=green]; 5 -> 3 [label="c",color=green]; 5 -> 4 [label="c",color=green]; 3 [shape=triangle,color=gray]; 4 [shape=triangle,color=gray]; 5 [shape=triangle,color=gray]; 2 [shape=doublecircle]; 3 [shape=doublecircle]; 4 [shape=doublecircle]; 1 [shape=circle]; }
Draws a graph specified as an adjacency list G.
gap> G := [[1,2,3],[5],[3,4],[1],[2,5]]; [ [ 1, 2, 3 ], [ 5 ], [ 3, 4 ], [ 1 ], [ 2, 5 ] ] gap> Print(DotStringForDrawingGraph(G)); digraph Graph__{ 1 -> 1 [style=bold, color=black]; 1 -> 2 [style=bold, color=black]; 1 -> 3 [style=bold, color=black]; 2 -> 5 [style=bold, color=black]; 3 -> 3 [style=bold, color=black]; 3 -> 4 [style=bold, color=black]; 4 -> 1 [style=bold, color=black]; 5 -> 2 [style=bold, color=black]; 5 -> 5 [style=bold, color=black]; 1 [shape=circle]; 2 [shape=circle]; 3 [shape=circle]; 4 [shape=circle]; 5 [shape=circle]; }
The dot code can be used to produce the following picture (which may also be produced by typing `DrawGraph(G);` \begin{center} \includegraphics[width=0.45\textwidth]{graph2.pdf} \end{center} <br><center><img src="graph2.jpg"></center><br> Draws automaton A and highlights it's strongly connected components by drawing the other edges in a dotted style.

The optional arguments state_names and L are as described in .
gap> rcg := Automaton("det",6,"ab",[ [ 3, 3, 6, 5, 6, 6 ], [ 4, 6, 2, 6, 4, 6 ] ], [ ],[ ]);; gap> Print(DotStringForDrawingSCCAutomaton(rcg)); digraph Automaton{ "1" -> "3" [label="a",color=red,style = dotted]; "2" -> "3" [label="a",color=red]; "3" -> "6" [label="a",color=red,style = dotted]; "4" -> "5" [label="a",color=red]; "5" -> "6" [label="a",color=red,style = dotted]; "6" -> "6" [label="a",color=red,style = dotted]; "1" -> "4" [label="b",color=blue,style = dotted]; "2" -> "6" [label="b",color=blue,style = dotted]; "3" -> "2" [label="b",color=blue]; "4" -> "6" [label="b",color=blue,style = dotted]; "5" -> "4" [label="b",color=blue]; "6" -> "6" [label="b",color=blue,style = dotted]; "1" [shape=circle, style=filled, fillcolor=white]; "2" [shape=circle, style=filled, fillcolor=white]; "3" [shape=circle, style=filled, fillcolor=white]; "4" [shape=circle, style=filled, fillcolor=white]; "5" [shape=circle, style=filled, fillcolor=white]; "6" [shape=circle, style=filled, fillcolor=white]; }
The dot code can be used to produce the following picture (which may also be produced by typing `DrawGraph(G);` \begin{center} \includegraphics[width=0.45\textwidth]{sccpoi2.pdf} \end{center} <br><center><img src="sccpoi2.jpg"></center><br>