Modeling infinity for the largest double value

Question

The question is about modeling infinity in C++ for the double data type. I need it in a header file, so we cannot use functions like numeric_limits

Answer 1

#include 
...
double d = INFINITY;

You can find INFINITY defined in (math.h):

A constant expression of type float representing positive or unsigned infinity, if available; else a positive constant of type float that overflows at translation time.