# std::log10(std::complex)

< cpp‎ | numeric‎ | complex

定义于头文件 `<complex>` |  |
template< class T > complex<T> log10( const complex<T>& z ); |  |

计算复数值 `z` 的复常用（底 10 ）对数，分支切割沿负实轴。

此函数的行为等价于 `std::log(z)/std::log(T(10))` 。

### 参数

z | - | 复数值

### 返回值

`z` 的复常用对数

### 示例

    #include <iostream>
    #include <cmath>
    #include <complex>

    int main()
    {
        std::complex<double> z(0, 1); // // r = 0, θ = pi/2
        std::cout << "2*log10" << z << " = " << 2.*std::log10(z) << '\n';

        std::complex<double> z2(sqrt(2)/2, sqrt(2)/2); // r = 1, θ = pi/4
        std::cout << "4*log10" << z2 << " = " << 4.*std::log10(z2) << '\n';

        std::complex<double> z3(-100, 0); // r = 100, θ = pi
        std::cout << "log10" << z3 << " = " << std::log10(z3) << '\n';
        std::complex<double> z4(-100, -0.0); // 切割的另一侧
        std::cout << "log10" << z4 << " (the other side of the cut) = "
                  << std::log10(z4) << '\n'
                  << "(note: pi/log(10) = " << acos(-1)/log(10) << ")\n";
    }

输出：

    2*log10(0,1) = (0,1.36438)
    4*log10(0.707107,0.707107) = (0,1.36438)
    log10(-100,0) = (2,1.36438)
    log10(-100,-0) (the other side of the cut) = (2,-1.36438)
    (note: pi/log(10) = 1.36438)

### 参阅

log(std::complex) | 沿负实轴切割的复自然对数 (函数模板)
log10 log10f log10l (C++11)(C++11) | 计算常用（以 10 为底）对数（ \({\small \log_{10}{x} }\)log10(x) ） (函数)
log10(std::valarray) | 应用函数 std::log10 到 valarray 的每个元素 (函数模板)