<cmath>

Huge value

A function returns this value when the result of a mathematical operation yields a value that is so large in magnitude that it is not representable with its return type. This is one of the possible range errors, and is signaled by setting errno to ERANGE.

Actually, functions can either return a positive or a negative HUGE_VAL (HUGE_VAL or -HUGE_VAL) to at least indicate the sign of the result.