在线文档教程
首页 技术教程 开发文档 觅分类 ICON图标
技术教程 开发文档 觅分类 ICON图标
Bootstrap 4
Bootstrap 3
C
C++
算法 | Algorithm
原子性操作 | Atomic operations
概念 | Concepts
容器 | Containers
动态内存管理 | Dynamic memory management
文件系统 | Filesystem
输入/输出 | Input/output
迭代器 | Iterator
关键词 | Keywords
语言 | Language
本土化 | Localizations
数字 | Numerics
beta
Common mathematical functions
Compile-time rational arithmetic
densities
densities
FE_ALL_EXCEPT
FE_DFL_ENV
FE_DIVBYZERO
FE_DOWNWARD
FE_INEXACT
FE_INVALID
FE_OVERFLOW
FE_TONEAREST
FE_TOWARDZERO
FE_UNDERFLOW
FE_UPWARD
Floating-point environment
FP_INFINITE
FP_NAN
FP_NORMAL
FP_SUBNORMAL
FP_ZERO
HUGE_VAL
HUGE_VALF
HUGE_VALL
INFINITY
Mathematical special functions
MATH_ERREXCEPT
math_errhandling
MATH_ERRNO
NAN
Numerics library
operators
operators
operators (std::bernoulli_distribution)
operators (std::bernoulli_distribution)
operators (std::binomial_distribution)
operators (std::binomial_distribution)
operators (std::cauchy_distribution)
operators (std::cauchy_distribution)
operators (std::chi_squared_distribution)
operators (std::chi_squared_distribution)
operators (std::complex)
operators (std::complex)
operators (std::discard_block_engine)
operators (std::discard_block_engine)
operators (std::discrete_distribution)
operators (std::discrete_distribution)
operators (std::exponential_distribution)
operators (std::exponential_distribution)
operators (std::extreme_value_distribution)
operators (std::extreme_value_distribution)
operators (std::fisher_f_distribution)
operators (std::fisher_f_distribution)
operators (std::gamma_distribution)
operators (std::gamma_distribution)
operators (std::geometric_distribution)
operators (std::geometric_distribution)
operators (std::independent_bits_engine)
operators (std::independent_bits_engine)
operators (std::linear_congruential_engine)
operators (std::linear_congruential_engine)
operators (std::lognormal_distribution)
operators (std::lognormal_distribution)
operators (std::mersenne_twister_engine)
operators (std::mersenne_twister_engine)
operators (std::negative_binomial_distribution)
operators (std::negative_binomial_distribution)
operators (std::normal_distribution)
operators (std::normal_distribution)
operators (std::piecewise_constant_distribution)
operators (std::piecewise_constant_distribution)
operators (std::piecewise_linear_distribution)
operators (std::piecewise_linear_distribution)
operators (std::poisson_distribution)
operators (std::poisson_distribution)
operators (std::shuffle_order_engine)
operators (std::shuffle_order_engine)
operators (std::student_t_distribution)
operators (std::student_t_distribution)
operators (std::subtract_with_carry_engine)
operators (std::subtract_with_carry_engine)
operators (std::uniform_int_distribution)
operators (std::uniform_int_distribution)
operators (std::uniform_real_distribution)
operators (std::uniform_real_distribution)
operators (std::valarray)
operators (std::weibull_distribution)
operators (std::weibull_distribution)
Pseudo-random number generation
RAND_MAX
std::abs(float)
std::abs(int)
std::abs(std::complex)
std::abs(std::valarray)
std::acos
std::acos(std::complex)
std::acos(std::valarray)
std::acosh
std::acosh(std::complex)
std::arg(std::complex)
std::asin
std::asin(std::complex)
std::asin(std::valarray)
std::asinh
std::asinh(std::complex)
std::assoc_laguerre
std::assoc_laguerref
std::assoc_laguerrel
std::assoc_legendre
std::assoc_legendref
std::assoc_legendrel
std::atan
std::atan(std::complex)
std::atan(std::valarray)
std::atan2
std::atan2(std::valarray)
std::atanh
std::atanh(std::complex)
std::begin(std::valarray)
std::bernoulli_distribution
std::bernoulli_distribution::bernoulli_distribution
std::bernoulli_distribution::max
std::bernoulli_distribution::min
std::bernoulli_distribution::p
std::bernoulli_distribution::param
std::bernoulli_distribution::reset
std::beta
std::betaf
std::betal
std::binomial_distribution
std::binomial_distribution::binomial_distribution
std::binomial_distribution::max
std::binomial_distribution::min
std::binomial_distribution::p
std::binomial_distribution::param
std::binomial_distribution::reset
std::cauchy_distribution
std::cauchy_distribution::a
std::cauchy_distribution::cauchy_distribution
std::cauchy_distribution::max
std::cauchy_distribution::min
std::cauchy_distribution::param
std::cauchy_distribution::reset
std::cbrt
std::ceil
std::chi_squared_distribution
std::chi_squared_distribution::chi_squared_distribution
std::chi_squared_distribution::max
std::chi_squared_distribution::min
std::chi_squared_distribution::n
std::chi_squared_distribution::param
std::chi_squared_distribution::reset
std::complex
std::complex::complex
std::complex::imag
std::complex::operators
std::complex::operators (unary)
std::complex::real
std::comp_ellint_1
std::comp_ellint_1f
std::comp_ellint_1l
std::comp_ellint_2
std::comp_ellint_2f
std::comp_ellint_2l
std::comp_ellint_3
std::comp_ellint_3f
std::comp_ellint_3l
std::conj(std::complex)
std::copysign
std::cos
std::cos(std::complex)
std::cos(std::valarray)
std::cosh
std::cosh(std::complex)
std::cosh(std::valarray)
std::cyl_bessel_i
std::cyl_bessel_if
std::cyl_bessel_il
std::cyl_bessel_j
std::cyl_bessel_jf
std::cyl_bessel_jl
std::cyl_bessel_k
std::cyl_bessel_kf
std::cyl_bessel_kl
std::cyl_neumann
std::cyl_neumannf
std::cyl_neumannl
std::discard_block_engine
std::discard_block_engine::base
std::discard_block_engine::discard
std::discard_block_engine::discard_block_engine
std::discard_block_engine::max
std::discard_block_engine::min
std::discard_block_engine::seed
std::discrete_distribution
std::discrete_distribution::discrete_distribution
std::discrete_distribution::max
std::discrete_distribution::min
std::discrete_distribution::param
std::discrete_distribution::probabilities
std::discrete_distribution::reset
std::div
std::ellint_1
std::ellint_1f
std::ellint_1l
std::ellint_2
std::ellint_2f
std::ellint_2l
std::ellint_3
std::ellint_3f
std::ellint_3l
std::end(std::valarray)
std::erf
std::erfc
std::exp
std::exp(std::complex)
std::exp(std::valarray)
std::exp2
std::expint
std::expintf
std::expintl
std::expm1
std::exponential_distribution
std::exponential_distribution::exponential_distribution
std::exponential_distribution::lambda
std::exponential_distribution::max
std::exponential_distribution::min
std::exponential_distribution::param
std::exponential_distribution::reset
std::extreme_value_distribution
std::extreme_value_distribution::a
std::extreme_value_distribution::extreme_value_distribution
std::extreme_value_distribution::max
std::extreme_value_distribution::min
std::extreme_value_distribution::param
std::extreme_value_distribution::reset
std::fabs
std::fdim
std::feclearexcept
std::fegetenv
std::fegetexceptflag
std::fegetround
std::feholdexcept
std::feraiseexcept
std::fesetenv
std::fesetexceptflag
std::fesetround
std::fetestexcept
std::feupdateenv
std::fisher_f_distribution
std::fisher_f_distribution::fisher_f_distribution
std::fisher_f_distribution::m
std::fisher_f_distribution::max
std::fisher_f_distribution::min
std::fisher_f_distribution::param
std::fisher_f_distribution::reset
std::floor
std::fma
std::fmax
std::fmin
std::fmod
std::fpclassify
std::frexp
std::gamma_distribution
std::gamma_distribution::alpha
std::gamma_distribution::gamma_distribution
std::gamma_distribution::max
std::gamma_distribution::min
std::gamma_distribution::param
std::gamma_distribution::reset
std::gcd
std::generate_canonical
std::geometric_distribution
std::geometric_distribution::geometric_distribution
std::geometric_distribution::max
std::geometric_distribution::min
std::geometric_distribution::p
std::geometric_distribution::param
std::geometric_distribution::reset
std::gslice
std::gslice_array
std::gslice_array::gslice_array
std::gslice_array::operators
std::hermite
std::hermitef
std::hermitel
std::hypot
std::ilogb
std::imag(std::complex)
std::imaxabs
std::independent_bits_engine
std::independent_bits_engine::base
std::independent_bits_engine::discard
std::independent_bits_engine::independent_bits_engine
std::independent_bits_engine::max
std::independent_bits_engine::min
std::independent_bits_engine::seed
std::indirect_array
std::indirect_array::indirect_array
std::indirect_array::operators
std::isfinite
std::isgreater
std::isgreaterequal
std::isinf
std::isless
std::islessequal
std::islessgreater
std::isnan
std::isnormal
std::isunordered
std::labs
std::laguerre
std::laguerref
std::laguerrel
std::lcm
std::ldexp
std::ldiv
std::legendre
std::legendref
std::legendrel
std::lgamma
std::linear_congruential_engine
std::linear_congruential_engine::discard
std::linear_congruential_engine::linear_congruential_engine
std::linear_congruential_engine::max
std::linear_congruential_engine::min
std::linear_congruential_engine::seed
std::literals::complex_literals::operators
std::llabs
std::lldiv
std::llrint
std::llround
std::log
std::log(std::complex)
std::log(std::valarray)
std::log10
std::log10(std::complex)
std::log10(std::valarray)
std::log1p
std::logb
std::lognormal_distribution
std::lognormal_distribution::lognormal_distribution
std::lognormal_distribution::m
std::lognormal_distribution::max
std::lognormal_distribution::min
std::lognormal_distribution::param
std::lognormal_distribution::reset
std::lrint
std::lround
std::mask_array
std::mask_array::mask_array
std::mask_array::operators
std::mersenne_twister_engine
std::mersenne_twister_engine::discard
std::mersenne_twister_engine::max
std::mersenne_twister_engine::mersenne_twister_engine
std::mersenne_twister_engine::min
std::mersenne_twister_engine::seed
std::modf
std::nan
std::nanf
std::nanl
std::nearbyint
std::negative_binomial_distribution
std::negative_binomial_distribution::max
std::negative_binomial_distribution::min
std::negative_binomial_distribution::negative_binomial_distribution
std::negative_binomial_distribution::p
std::negative_binomial_distribution::param
std::negative_binomial_distribution::reset
std::nextafter
std::nexttoward
std::norm(std::complex)
std::normal_distribution
std::normal_distribution::max
std::normal_distribution::mean
std::normal_distribution::min
std::normal_distribution::normal_distribution
std::normal_distribution::param
std::normal_distribution::reset
std::piecewise_constant_distribution
std::piecewise_constant_distribution::intervals
std::piecewise_constant_distribution::max
std::piecewise_constant_distribution::min
std::piecewise_constant_distribution::param
std::piecewise_constant_distribution::piecewise_constant_distribution
std::piecewise_constant_distribution::reset
std::piecewise_linear_distribution
std::piecewise_linear_distribution::intervals
std::piecewise_linear_distribution::max
std::piecewise_linear_distribution::min
std::piecewise_linear_distribution::param
std::piecewise_linear_distribution::piecewise_linear_distribution
std::piecewise_linear_distribution::reset
std::poisson_distribution
std::poisson_distribution::max
std::poisson_distribution::mean
std::poisson_distribution::min
std::poisson_distribution::param
std::poisson_distribution::poisson_distribution
std::poisson_distribution::reset
std::polar(std::complex)
std::pow
std::pow(std::complex)
std::pow(std::valarray)
std::proj(std::complex)
std::rand
std::random_device
std::random_device::entropy
std::random_device::max
std::random_device::min
std::random_device::random_device
std::ratio
std::ratio_add
std::ratio_divide
std::ratio_equal
std::ratio_greater
std::ratio_greater_equal
std::ratio_less
std::ratio_less_equal
std::ratio_multiply
std::ratio_not_equal
std::ratio_subtract
std::real(std::complex)
std::remainder
std::remquo
std::riemann_zeta
std::riemann_zetaf
std::riemann_zetal
std::rint
std::round
std::scalbln
std::scalbn
std::seed_seq
std::seed_seq::generate
std::seed_seq::param
std::seed_seq::seed_seq
std::seed_seq::size
std::shuffle_order_engine
std::shuffle_order_engine::base
std::shuffle_order_engine::discard
std::shuffle_order_engine::max
std::shuffle_order_engine::min
std::shuffle_order_engine::seed
std::shuffle_order_engine::shuffle_order_engine
std::signbit
std::sin
std::sin(std::complex)
std::sin(std::valarray)
std::sinh
std::sinh(std::complex)
std::sinh(std::valarray)
std::slice
std::slice_array
std::slice_array::operators
std::slice_array::slice_array
std::sph_bessel
std::sph_besself
std::sph_bessell
std::sph_legendre
std::sph_legendref
std::sph_legendrel
std::sph_neumann
std::sph_neumannf
std::sph_neumannl
std::sqrt
std::sqrt(std::complex)
std::sqrt(std::valarray)
std::srand
std::student_t_distribution
std::student_t_distribution::max
std::student_t_distribution::min
std::student_t_distribution::n
std::student_t_distribution::param
std::student_t_distribution::reset
std::student_t_distribution::student_t_distribution
std::subtract_with_carry_engine
std::subtract_with_carry_engine::discard
std::subtract_with_carry_engine::max
std::subtract_with_carry_engine::min
std::subtract_with_carry_engine::seed
std::subtract_with_carry_engine::subtract_with_carry_engine
std::swap(std::valarray)
std::tan
std::tan(std::complex)
std::tan(std::valarray)
std::tanh
std::tanh(std::complex)
std::tanh(std::valarray)
std::tgamma
std::trunc
std::uniform_int_distribution
std::uniform_int_distribution::a
std::uniform_int_distribution::max
std::uniform_int_distribution::min
std::uniform_int_distribution::param
std::uniform_int_distribution::reset
std::uniform_int_distribution::uniform_int_distribution
std::uniform_real_distribution
std::uniform_real_distribution::a
std::uniform_real_distribution::max
std::uniform_real_distribution::min
std::uniform_real_distribution::param
std::uniform_real_distribution::reset
std::uniform_real_distribution::uniform_real_distribution
std::valarray
std::valarray::apply
std::valarray::cshift
std::valarray::max
std::valarray::min
std::valarray::operators
std::valarray::operators
std::valarray::operator[]
std::valarray::resize
std::valarray::shift
std::valarray::size
std::valarray::sum
std::valarray::swap
std::valarray::valarray
std::weibull_distribution
std::weibull_distribution::a
std::weibull_distribution::max
std::weibull_distribution::min
std::weibull_distribution::param
std::weibull_distribution::reset
std::weibull_distribution::weibull_distribution
stddev
规律表达 | Regular expressions
标准库头文件 | Standard library header files
字符串 | Strings
线程支持 | Thread support
应用 | Utilities
Clojure 1.8
Codeigniter 3
CSS
Docker 17
Electron
Elixir 1.5
Erlang 20
Eslint
Express
Git
Go
HTML
HTTP
Immutable 3.8.1
JavaScript
Lodash 4
Lua 5.3
Nginx
PHP
Phpunit 6
Python
React
React native
Redis
Redux
Ruby 2.4
Sass
Scikit image
Socket.IO
Sqlite
SVG
TensorFlow Guide
Typescript
Underscore
Vue 2
Webpack
Xslt & Xpath
Yarn
RxJS 5
Rollup.js
Babel
Parcel
MobX
Koa
Angular
Gulp
Grunt
Stylelint
Standard JS
Element UI
iView UI
Lavas
Mint UI
PostCSS
ThinkJS
Nest
npm
Node.js教程
JSON教程
Groovy教程
vb.net教程
Storm入门教程
Hibernate 教程
Slick教程
MongoDB教程
Yii 2.0

std::log2

STD：：Log2

Defined in header ​​
float log2( float arg (1)(since C++11)
double log2( double arg (2)(since C++11)
long double log2( long double arg (3)(since C++11)
double log2( Integral arg (4)(since C++11)

1-3%29计算二进制%28碱基-二%29对数arg...

4%29一组过载或接受任意参数的函数模板积分型等于2%29%28double29%。

参数

arg-value of floating-point or Integral type

返回值

如果没有错误发生，基地-二对数arg%28日志

返回2%28 arg%29或lb%28 arg%29%29。

如果发生域错误，则返回支持%29的实现定义值%28 NaN。

如果发生极差，-HUGE_VAL，，，-HUGE_VALF，或-HUGE_VALL会被归还。

错误处理

错误按数学[医]错误处理...

在以下情况下发生域错误arg小于零。

极错误可能发生在arg是零。

如果实现支持ieee浮点算法%28IEC 60559%29，

  • 如果参数为±0，则返回-∞FE_DIVBYZERO是被抚养的。

  • 如果参数为1，则返回+0。

  • 如果参数为否定，则返回NaNFE_INVALID是被抚养的。

  • 如果参数为+∞，则返回+∞

  • 如果参数为nan，则返回nan。

注记

整型arg，二进制对数可以解释为输入中最重要的1位的基于零的索引。

例

二次

#include <iostream>
#include <cmath>
#include <cerrno>
#include <cstring>
#include <cfenv>
#pragma STDC FENV_ACCESS ON
int main()
{
    std::cout << "log2(65536) = " << std::log2(65536) << '\n'
              << "log2(0.125) = " << std::log2(0.125) << '\n'
              << "log2(0x020f) = " << std::log2(0x020f)
              << " (highest set bit is in position 9)\n"
              << "base-5 logarithm of 125 = " << std::log2(125)/std::log2(5) << '\n';
    // special values
    std::cout << "log2(1) = " << std::log2(1) << '\n'
              << "log2(+Inf) = " << std::log2(INFINITY) << '\n';
    // error handling 
    errno=0; std::feclearexcept(FE_ALL_EXCEPT
    std::cout << "log2(0) = " << std::log2(0) << '\n';
    if(errno == ERANGE)
        std::cout << "    errno == ERANGE: " << std::strerror(errno) << '\n';
    if(std::fetestexcept(FE_DIVBYZERO))
        std::cout << "    FE_DIVBYZERO raised\n";
}

二次

可能的产出：

二次

log2(65536) = 16
log2(0.125) = -3
log2(0x020f) = 9.04166 (highest set bit is in position 9)
base-5 logarithm of 125 = 3
log2(1) = 0
log2(+Inf) = inf
log2(0) = -inf
    errno == ERANGE: Numerical result out of range
    FE_DIVBYZERO raised

二次

另见

logcomputes natural (base e) logarithm (to base e) (ln(x)) (function)
log10computes common (base 10) logarithm (log10(x)) (function)
log1p (C++11)natural logarithm (to base e) of 1 plus the given number (ln(1+x)) (function)
exp2 (C++11)returns 2 raised to the given power (2x) (function)

c日志文件2

 © cppreference.com

在CreativeCommonsAttribution下授权-ShareAlike未移植许可v3.0。

http：//en.cppreference.com/w/cpp/数值/数学/log 2

  • 黔ICP备2021005045号