logb, logbf, logbl, _logb, _logbf
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Extracts the exponent value of a floating-point argument.
double logb( double x ); float logb( float x ); // C++ only long double logb( long double x ); // C++ only float logbf( float x ); long double logbl( long double x ); double _logb( double x ); float _logbf( float x );
Parameters
x
A floating-point value.
logb returns the unbiased exponent value of x as a signed integer represented as a floating-point value.
The logb functions extract the exponential value of the floating-point argument x, as though x were represented with infinite range. If the argument x is denormalized, it is treated as if it were normalized.
Because C++ allows overloading, you can call overloads of logb that take and return float or long double values. In a C program, logb always takes and returns a double.
| Input | SEH exception | Matherr exception |
|---|---|---|
| ± QNAN,IND | None | _DOMAIN |
| ± 0 | ZERODIVIDE | _SING |
| Routine | Required header |
|---|---|
_logb | <float.h> |
logb, logbf, logbl, _logbf | <math.h> |
For more compatibility information, see Compatibility.
All versions of the C run-time libraries.
Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.