ilogb, ilogbf, ilogbl

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Retrieves an integer that represents the unbiased base-2 exponent of the specified value.

Syntax

int ilogb(  
   double x  
);  
  
int ilogb(  
   float x  
); //C++ only  
  
int ilogb(  
   long double x  
); //C++ only  
  
int ilogbf(  
   float x  
);  
  
int ilogbl(  
   long double x  
);  
  

Parameters

[in] x
The specified value.

Return Value

If successful, return the base-2 exponent of x as a signed int value.

Otherwise, returns one of the following values, defined in <math.h>:

Errors are reported as specified in _matherr.

Remarks

Because C++ allows overloading, you can call overloads of ilogb that take and return float and long double types. In a C program, ilogb always takes and returns a double.

Calling this function is similar to calling the equivalent logb function, then casting the return value to int.

Requirements

For additional compatibility information, see Compatibility.

See Also

Alphabetical Function Reference
frexp
logb, logbf, logbl, _logb, _logbf