public Value( String strVal ) {
      value = strVal;
      
      // test to see which type of value it is
      if       ( value.compareTo("#t") == 0 || value.compareTo("#f") == 0) {
         type = "boolean";
      }
      else if  ( value.matches("-?\\d+") ) {
         type = "integer";
      }
      else if  ( value.matches("-?\\d*.\\d+") ) {
         type = "decimal";
      }
      else if  ( value.startsWith("\"") && value.endsWith("\"") ) {
         type = "string";
      }
      else {
         // you should never get here if called from interp()
         System.err.println("Error in Value Constructor: Unknown Type '" + strVal + "'");
         type = "undefined";
      }
   }