log2, log2f, log2l - base-2 logarithmic function

Attributes

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ log2(), log2f(), log2l()                                                    │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

Description

       These functions return the base-2 logarithm of x.

Errors

       See  math_error(7)  for  information on how to determine whether an error has occurred when calling these
       functions.

       For a discussion of the errors that can occur for these functions, see log(3).

History

       glibc 2.1.  C99, POSIX.1-2001.

       The variant returning double also conforms to SVr4, 4.3BSD.

Library

       Math library (libm, -lm)

Name

       log2, log2f, log2l - base-2 logarithmic function

Return Value

       On success, these functions return the base-2 logarithm of x.

       For special cases, including where x is 0, 1, negative, infinity, or NaN, see log(3).

Standards

       C11, POSIX.1-2008.

Synopsis

#include<math.h>doublelog2(doublex);floatlog2f(floatx);longdoublelog2l(longdoublex);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       log2(), log2f(), log2l():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L