etnbrd/flx-compiler

digraph G {

  graph [ fontname="HelveticaNeue-Thin", fontcolor=black, fontsize=20 ];
  node [ fontname="HelveticaNeue-Thin", fontcolor=black, fontsize=20, penwidth=0.5 shape=circle, fixedsize=true, width=1.2, height=1.2 ];
  edge [ fontname="HelveticaNeue-Thin", fontcolor=black, fontsize=20, penwidth=0.5 splines=line, arrowsize=0.7 ];

  plus [label="+"]
  ab [label="a,b"]   45 [label="4,5"]   ab [label="a,b"] 

  ab -> plus;
  plus -> return;
  return -> c;
  45 -> ab;
}