A solution to the definition and determination of the invalid value of C + + floating-point number _c language

In the actual calculation may appear the floating-point type invalid data, the format output to the file content is 1.79769e+308, the output to the interface is a very big string of data. Either way, it's not easy to read and find.
Invalid values are defined as follows: #define INVALIDDOUBLE * (double*) ("\xff\xff\xff\xff\xff\xff\xef\x7f")
Double Price;
......... (Calculated step omitted)
Price=getprice (); Get Data

To determine the floating-point data in the following way
(price==invaliddouble)? 0:price