public void addColumn(String name,String expr){
  Expression ex=ExpressionParser.parse(expr);
  Throwable t=ExpressionParser.getError();
  if (t != null) {
    throw new RuntimeException(t);
  }
 else {
    addColumn(name,ex);
  }
}

public void addColumn ( String name , String expr ) { Expression ex = ExpressionParser . parse ( expr ) ; Throwable t = ExpressionParser . getError ( ) ; if ( t != null ) { throw new RuntimeException ( t ) ; } else { addColumn ( name , ex ) ; } }
add a derived column to this table , using an expression instance to dynamically calculate the column data values .
