error: expected primary-expression before ‘double’

Question

#include <iostream> 
#include <complex>

using namespace std;

class MyComplex{
  private:
    int real, img;

  public:
    MyComplex();
    MyComplex(int,int);
    ~MyComplex();
    void set(int,int);
    void display();
};

MyComplex::MyComplex(){
  cout << "i'm being constructed (default).\n";
  real=img=0;
}

MyComplex::MyComplex(int r, int i){
  cout << "i'm being constructed (parameterized).\n";
  real=r;
  img=i;
}

MyComplex::~MyComplex(){
  cout << "I'm being destroyed\n";
}

void MyComplex::set(int r, int i){
  real=r;
  img=i;
}

void MyComplex::display(){
  cout << real << "+i" << img << endl;
}



int main(){
  MyComplex c1;
  MyComplex c2(10,-8);
  c1.set(2,9);
  c1.display();
  c2.display();

  cout << "Magnitude"<< double abs(const complex) << endl;
}

First time in these forums, I apologize if my code is horribly written, I am but a beginner.

I found an assignment on a book the requires you to calculate the magnitude of the complex numbers.

I am getting this error:

testcomplex.cpp: In function ‘int main()’:
testcomplex.cpp:50:25: ***error: expected primary-expression before ‘double’
   cout << "Magnitude"<< double abs(const complex) << endl;***

Solution

You seem to have written the function's declaration instead of calling it. Assuming you actually have a function called abs, you can call it by simply passing a variable to it in it's brackets:

cout << "Magnitude " << abs(c1) << endl;

Comments

[rcs]

have you tried changing it to abs(complex)?

[Biffen]

What is a double doing there anyway?!

[John Zwinck]

double abs(const complex) makes no sense at all. What is it trying to do?

[juanchopanza]

You are trying to print a function declaration. That doesn't make much sense.