complex<double>

描述一个对象，该对象存储两个都为 double 类型的有序对象对，该有序对中的第一个对象表示复数的实部，第二个对象表示复数虚部。

语法

template <>
class complex<double> {
public:
    constexpr complex(
    double RealVal = 0,
    double ImagVal = 0);

constexpr complex(const complex<double>& complexNum);

constexpr explicit complex(const complex<long double>& complexNum);
// rest same as class template complex
};

参数

RealVal
正在构造的复数实部的 double 类型值。

ImagVal
正在构造的复数虚部的 double 类型值。

complexNum
类型为 float 或 long double 的复数，其实部和虚部用于初始化正在构造的 double 类型的复数。

返回值

double 类型的复数。

注解

类模板 complex 显式专用化为 double 类型的 complex 类仅与它所定义构造函数中的类模板不同。 从 float 到 double 类型的转换可以是隐式的，但从 long double 到 double 的转换必须是 explicit。 使用 explicit 转换可取消在最初使用赋值语法进行类型转换。

有关 complex 类模板的详细信息，请参阅 complex 类。 有关 complex 类模板的成员列表，请参阅。

示例

// complex_comp_dbl.cpp
// compile with: /EHsc
#include <complex>
#include <iostream>

int main( )
{
   using namespace std;
   double pi = 3.14159265359;

   // The first constructor specifies real & imaginary parts
   complex <double> c1 ( 4.0 , 5.0 );
   cout << "Specifying initial real & imaginary parts,\n"
        << "as type double gives c1 = " << c1 << endl;

   // The second constructor initializes values of the real &
   // imaginary parts using those of complex number of type float
   complex <float> c2float ( 4.0 , 5.0 );
   complex <double> c2double ( c2float );
   cout << "Implicit conversion from type float to type double,"
        << endl << "gives c2double = " << c2double << endl;

   // The third constructor initializes values of the real &
   // imaginary parts using those of a complex number
   // of type long double
   complex <long double> c3longdouble ( 4.0 , 5.0 );
   complex <double> c3double ( c3longdouble );
   cout << "Explicit conversion from type float to type double,"
        << endl << "gives c3longdouble = " << c3longdouble << endl;

   // The modulus and argument of a complex number can be recovered
   double absc3 = abs ( c3longdouble );
   double argc3 = arg ( c3longdouble );
   cout << "The modulus of c3 is recovered from c3 using: abs ( c3 ) = "
        << absc3 << endl;
   cout << "Argument of c3 is recovered from c3 using:" << endl
        << "arg ( c3 ) = " << argc3 << " radians, which is "
        << argc3 * 180 / pi << " degrees." << endl;
}
/* Output:
Specifying initial real & imaginary parts,
as type double gives c1 = (4,5)
Implicit conversion from type float to type double,
gives c2double = (4,5)
Explicit conversion from type float to type double,
gives c3longdouble = (4,5)
The modulus of c3 is recovered from c3 using: abs ( c3 ) = 6.40312
Argument of c3 is recovered from c3 using:
arg ( c3 ) = 0.896055 radians, which is 51.3402 degrees.
*/

要求

标头：<complex>

命名空间： std

另请参阅

complex 类
C++ 标准库中的线程安全