code: ///////////////////////////////////////////////////////////////////////////////
  // For information as to what this class does, see the Javadoc, below.       //
  // Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
  // 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
  // Ramsey, and Clark Glymour.                                                //
  //                                                                           //
  // This program is free software; you can redistribute it and/or modify      //
  // it under the terms of the GNU General Public License as published by      //
  // the Free Software Foundation; either version 2 of the License, or         //
  // (at your option) any later version.                                       //
  //                                                                           //
  // This program is distributed in the hope that it will be useful,           //
  // but WITHOUT ANY WARRANTY; without even the implied warranty of            //
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
  // GNU General Public License for more details.                              //
  //                                                                           //
  // You should have received a copy of the GNU General Public License         //
  // along with this program; if not, write to the Free Software               //
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
  ///////////////////////////////////////////////////////////////////////////////
  
  package edu.cmu.tetrad.graph;
  
  import java.util.StringTokenizer;
  
  /**
   * Converts graphs used in the search package from one type to another.
   *
   * @author Donald Crimbchin
   * @author Joseph Ramsey
   */
  public final class GraphConverter {
  
      /**
       * Converts a string spec of a graph--for example, "X1-->X2, X1---X3,
       * X2o->X4, X3<->X4" to a Graph. The spec consists of a comma separated list
       * of edge specs of the forms just used in the previous sentence.
       * Unconnected nodes may be listed separately--example: "X,Y->Z". To specify
       * a node as latent, use "Latent()." Example: "Latent(L1),Y->L1".
       */
      public static Graph convert(String spec) {
          Graph graph = new EdgeListGraph();
          StringTokenizer st1, st2;
  
          for (st1 = new StringTokenizer(spec, ", "); st1.hasMoreTokens(); ) {
              String edgeSpec = st1.nextToken();
  
              st2 = new StringTokenizer(edgeSpec, "<>-o ");
  
              String var1 = st2.nextToken();
  
              if (var1.startsWith("Latent(")) {
                  String latentName =
                          (String) var1.subSequence(7, var1.length() - 1);
                  GraphNode node = new GraphNode(latentName);
                  node.setNodeType(NodeType.LATENT);
                  graph.addNode(node);
                  continue;
              }
  
              if (!st2.hasMoreTokens()) {
                  graph.addNode(new GraphNode(var1));
                  continue;
              }
  
              String var2 = st2.nextToken();
  
              if (graph.getNode(var1) == null) {
                  graph.addNode(new GraphNode(var1));
              }
  
              if (graph.getNode(var2) == null) {
                  graph.addNode(new GraphNode(var2));
              }
  
              Node nodeA = graph.getNode(var1);
              Node nodeB = graph.getNode(var2);
              Edge edge = graph.getEdge(nodeA, nodeB);
  
              if (edge != null) {
                  throw new IllegalArgumentException(
                          "Multiple edges connecting " +
                                  "nodes is not supported.");
              }
  
              if (edgeSpec.lastIndexOf("-->") != -1) {
                  graph.addDirectedEdge(nodeA, nodeB);
              }
  
              if (edgeSpec.lastIndexOf("<--") != -1) {
                  graph.addDirectedEdge(nodeB, nodeA);
              } else if (edgeSpec.lastIndexOf("---") != -1) {
                  graph.addUndirectedEdge(nodeA, nodeB);
              } else if (edgeSpec.lastIndexOf("<->") != -1) {
                  graph.addBidirectedEdge(nodeA, nodeB);
              } else if (edgeSpec.lastIndexOf("o->") != -1) {
                  graph.addPartiallyOrientedEdge(nodeA, nodeB);
              } else if (edgeSpec.lastIndexOf("<-o") != -1) {
                  graph.addPartiallyOrientedEdge(nodeB, nodeA);
              } else if (edgeSpec.lastIndexOf("o-o") != -1) {
                  graph.addNondirectedEdge(nodeB, nodeA);
              }
          }
  
          return graph;
      }
  }
  
  
  
  
  
  