cpp/numeric/math/fpclassify

@1@ Categorizes floating point value into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category. @A@ Additional overloads are provided for all integer types, which are treated as.

Return value
one of fp_infinite, fp_nan, fp_normal, fp_subnormal, fp_zero or implementation-defined type, specifying the category of.