Question

I was reading Setting an int to Infinity in C++. I understand that when one needs true infinity, one is supposed to use numeric_limits<float>::infinity(); I guess the rationale behind it is that usually integral types have no values designated for representing special states like NaN, Inf, etc. like IEEE 754 floats do (again C++ doesn’t mandate neither – int & float used are left to the implementation); but still it’s misleading that max > infinity for a given type. I’m trying to understand the rationale behind this call in the standard. If having infinity doesn’t make sense for a type, then shouldn’t it be disallowed instead of having a flag to be checked for its validity?

Answer 1

The function numeric_limits<T>::infinity() makes sense for those T for which numeric_limits<T>::has_infinity returns true.

In case of T=int, it returns false. So that comparison doesn’t make sense, because numeric_limits<int>::infinity() does not return any meaningful value to compare with.