private void print_map() {
      char ch=' ';
      int r,c;

      System.out.println();
      for( r=0; r < nrows; r++ ) {
         for( c=0; c < map[r].length; c++ ) {
            if(( r == row )&&( c == col )) { // agent is here
               switch( dirn ) {
                case NORTH: ch = '^'; break;
                case EAST:  ch = '>'; break;
                case SOUTH: ch = 'v'; break;
                case WEST:  ch = '<'; break;
               }
            }
            else {
              ch = map[r][c];
            }
            System.out.print( ch );
         }
         System.out.println();
      }
      System.out.println();
   }