From 82ba818ff456bcd6d56a06226e3f27e98fbb55c3 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Thu, 14 Aug 2025 22:58:58 -0500 Subject: removing all downloaded devdocs files --- devdocs/c/numeric%2Fmath%2Flog2.html | 85 ------------------------------------ 1 file changed, 85 deletions(-) delete mode 100644 devdocs/c/numeric%2Fmath%2Flog2.html (limited to 'devdocs/c/numeric%2Fmath%2Flog2.html') diff --git a/devdocs/c/numeric%2Fmath%2Flog2.html b/devdocs/c/numeric%2Fmath%2Flog2.html deleted file mode 100644 index 14c569b3..00000000 --- a/devdocs/c/numeric%2Fmath%2Flog2.html +++ /dev/null @@ -1,85 +0,0 @@ -

log2, log2f, log2l

Defined in header <math.h> 
float       log2f( float arg );
-		 (1) (since C99) 
double      log2( double arg );
-		 (2) (since C99) 
long double log2l( long double arg );
-		 (3) (since C99)
Defined in header <tgmath.h> 
#define log2( arg )
-		 (4) (since C99)
-1-3) Computes the base 2 logarithm of arg.
-4) Type-generic macro: If arg has type long double, log2l is called. Otherwise, if arg has integer type or the type double, log2 is called. Otherwise, log2f is called.

Parameters

- -
arg - floating point value

Return value

If no errors occur, the base-2 logarithm of arg (log2(arg) or lb(arg)) is returned.

-

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

-

If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.

-

Error handling

Errors are reported as specified in math_errhandling.

-

Domain error occurs if arg is less than zero.

-

Pole error may occur if arg is zero.

-

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

-

Notes

For integer arg, the binary logarithm can be interpreted as the zero-based index of the most significant 1 bit in the input.

-

Example

#include <stdio.h>
-#include <math.h>
-#include <float.h>
-#include <errno.h>
-#include <fenv.h>
-// #pragma STDC FENV_ACCESS ON
-int main(void)
-{
-    printf("log2(65536) = %f\n", log2(65536));
-    printf("log2(0.125) = %f\n", log2(0.125));
-    printf("log2(0x020f) = %f (highest set bit is in position 9)\n", log2(0x020f));
-    printf("base-5 logarithm of 125 = %f\n", log2(125)/log2(5));
-    // special values
-    printf("log2(1) = %f\n", log2(1));
-    printf("log2(+Inf) = %f\n", log2(INFINITY));
-    //error handling
-    errno = 0; feclearexcept(FE_ALL_EXCEPT);
-    printf("log2(0) = %f\n", log2(0));
-    if(errno == ERANGE) perror("    errno == ERANGE");
-    if(fetestexcept(FE_DIVBYZERO)) puts("    FE_DIVBYZERO raised");
-}

Possible output:

-
log2(65536) = 16.000000
-log2(0.125) = -3.000000
-log2(0x020f) = 9.041659 (highest set bit is in position 9)
-base-5 logarithm of 125 = 3.000000
-log2(1) = 0.000000
-log2(+Inf) = inf
-log2(0) = -inf
-    errno == ERANGE: Numerical result out of range
-    FE_DIVBYZERO raised

References

See also

- - - - -
-
(C99)(C99)
 computes natural (base-e) logarithm (\({\small \ln{x} }\)ln(x))
(function)
-
(C99)(C99)
 computes common (base-10) logarithm (\({\small \log_{10}{x} }\)log10(x))
(function)
-
(C99)(C99)(C99)
 computes natural (base-e) logarithm of 1 plus the given number (\({\small \ln{(1+x)} }\)ln(1+x))
(function)
-
(C99)(C99)(C99)
 computes 2 raised to the given power (\({\small 2^x}\)2x)
(function)
C++ documentation for log2
-

- © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
- https://en.cppreference.com/w/c/numeric/math/log2 -

-
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