Resolve the definition of invalid C ++ floating point numbers and the summary of the determination of invalid values

In actual computation, invalid floating point data may occur. The formatted output content to the file is 1.79769e + 308, and the output to the interface is a large string of data. Either of the two methods is not very convenient for reading and searching. It is worthwhile to judge whether the floating point data is invalid during development.

Invalid value definitionAs follows:
# Define InvalidDouble * (double *) ("\ xff \ xef \ x7f ")
Double price;
...... (The calculation step is omitted)
Price = GetPrice (); // get data

Use the following methodHow to determine Invalid Data
(Price = InvalidDouble )? 0: price