C++ <cmath> - FP_ILOGB0, FP_ILOGBNAN
The C++ <cmath> ilogb() function returns the integer part of the logarithm of |x| (mod of argument), using FLT_RADIX as base for the logarithm. On most platforms, FLT_RADIX is 2.
In special cases, macros - FP_ILOGB0 and FP_ILOGBNAN are returned by this function:
| Macros | Description |
|---|---|
| FP_ILOGB0 | Returned when x is zero. |
| FP_ILOGBNAN | Returned when x is NaN. |
Example:
Lets consider example below to understand macros - FP_ILOGB0 and FP_ILOGBNAN.
#include <iostream>
#include <cmath>
using namespace std;
int main (){
//returned value when argument is zero
cout<<"ilogb(0) = "<<ilogb(0)<<"\n";
cout<<"FP_ILOGB0 = "<<FP_ILOGB0<<"\n";
cout<<endl;
//returned value when argument is NaN
cout<<"ilogb(sqrt(-1)) = "<<ilogb(sqrt(-1))<<"\n";
cout<<"FP_ILOGBNAN = "<<FP_ILOGBNAN<<"\n";
return 0;
}
The output of the above code will be:
ilogb(0) = -2147483648 FP_ILOGB0 = -2147483648 ilogb(sqrt(-1)) = -2147483648 FP_ILOGBNAN = -2147483648
❮ C++ <cmath> Library
