复杂 <double> 在C ++中-不能使用imag（），complex（），real（）

Question

I have a problem when using functions from the complex.h I have some numbers

typedef complex<double> cmplx;
cmplx N;
double x;
double y;

and now I need operations over them:

double k = real(N);
cmplx NI = complex(x,y);
double l = imag(N);

nothing from these works. What's wrong? I have tried to write creal, cimag, but nothing works... The compiler writes:

error: argument list for class template "std::complex" is missing

Please for your help

Thanks

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EDIT

Thank you again for your help but now I have a new problem. If I have an array Arr[N] of cmplx numbers and now I need the real part of the Arr[i] I have written

realArray[5] = ComplexArray[5].real();

I get an error:

error: expression must have class type

the error is the same for real() or imag() functions

Answer 1

I have a problem when using functions from the complex.h

There is no standard header with that name. I'll assume you mean <complex> ; otherwise, you're including either a prehistoric or non-standard library, or the C library. In any case, you should change to <complex> .

The first and third lines should be fine. real and imag are defined both as non-member functions usable as you use them, or as member functions usable as N.real() and N.imag() .

The second line should be one of:

cmplx NI = cmplx(x,y);
cmplx NI = complex<double>(x,y);
cmplx NI(x,y);

either using your type alias cmplx , or the template specialisation itself, to specify the type. As the error says, you can't use a template where you need a type.

Answer 2

You want something like this:

double k = N.real();
cmplx NI = cmplx(x,y);
double l = N.imag();