/*
 * call-seq:
 *    res.fformat( column_number ) -> Fixnum
 *
 * Returns the format (0 for text, 1 for binary) of column
 * _column_number_.
 * 
 * Raises ArgumentError if _column_number_ is out of range.
 */
static VALUE
pgresult_fformat(VALUE self, VALUE column_number)
{
    PGresult *result = get_pgresult(self);
    int fnumber = NUM2INT(column_number);
    if (fnumber < 0 || fnumber >= PQnfields(result)) {
        rb_raise(rb_eArgError, "Column number is out of range: %d", 
            fnumber);
    }
    return INT2FIX(PQfformat(result, fnumber));
}