`complex<double>`

Article
12/06/2021

Describes an object that stores an ordered pair of objects both of type double, the first representing the real part of a complex number and the second representing the imaginary part.

Syntax

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
};

Parameters

RealVal
The value of type double for the real part of the complex number being constructed.

ImagVal
The value of type double for the imaginary part of the complex number being constructed.

complexNum
The complex number of type float or of type long double whose real and imaginary parts are used to initialize a complex number of type double being constructed.

Return Value

A complex number of type double.

Remarks

The explicit specialization of the class template complex to a complex class of type double differs from the class template only in the constructors it defines. The conversion from float to double is allowed to be implicit, but the conversion from long double to double is required to be explicit. The use of explicit rules out the initiation with type conversion using assignment syntax.

For more information on the class template complex, see complex Class. For a list of members of the class template complex, see .

Example

// 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.
*/

Requirements

Header: <complex>

Namespace: std