log2, log2f, log2l
Visual Studio 2015
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Determines the binary (base-2) logarithm of the specified value.
double log2( double x ); float log2( float x ); //C++ only long double log2( long double x ); //C++ only float log2f( float x ); long double log2l( long double x );
Parameters
[in] x
The value to determine the base-2 logarithm of.
On success, returns return log2 x.
Otherwise, may return one of the following values:
| Issue | Return |
|---|---|
x < 0 | NaN |
x = ±0 | -INFINITY |
x = 1 | +0 |
| +INFINITY | +INFINITY |
| NaN | NaN |
| domain error | NaN |
| pole error | -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL |
Errors are reported as specified in _matherr.
If x is an integer, this function essentially returns the zero-based index of the most significant 1 bit of x.
| Function | C header | C++ header |
|---|---|---|
log2, log2f, log2l | <math.h> | <cmath> |
For additional compatibility information, see Compatibility.
Alphabetical Function Reference
exp2, exp2f, exp2l
log, logf, log10, log10f
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