code: public VarDefBuilder varDefAtPath( String[] path)
      {
      VarDefBuilder varDefBuilder = null;
      if( path != null && path.length > 0)
        {
        String varDefName = path[ path.length - 1];
        VarSetBuilder parentBuilder = varSetAtPath( Arrays.copyOfRange( path, 0, path.length - 1));
        if( parentBuilder != null)
          {
          varDefBuilder = parentBuilder.varDefAtPath( varDefName);
          }
        else
          {
          VarDef varDef = new VarDef( varDefName);
          varSet_.addMember( varDef);
          varDefBuilder = new VarDefBuilder( varDef);
          }
        }
  
      return varDefBuilder;
      }
docs: Adds a new {@link VarDef} with the given path name and returns a builder
  for the new <CODE>VarDef</CODE>.