According to http://www.cplusplus.com/reference/complex/complex/complex/, class complex<double> has a default construct of the form complex (double re = 0.0, double im = 0.0);. However, I don't know if this is really correct. Could anyone explain the strange behavior of the code below?
#include <iostream>
#include <complex>
#include <typeinfo>
using namespace std;
int main() {
complex<double> cmp1(1, 2);
complex<double> cmp2(1); //isn't the same as cmp2(1, 0.0) ?
complex<double> cmp3(); //isn't the same as cmp3(0.0, 0.0) ?
cout << cmp1.real() << "\n"; //=> 1
cout << cmp1.imag() << "\n"; //=> 2
cout << cmp2.real() << "\n"; //=> 1
cout << cmp2.imag() << "\n"; //=> 0
//cout << cmp3.real() << "\n"; //error (why?) //mark1
//cout << cmp3.imag() << "\n"; //error (why?)
/* error message output by `mark1`: */
/* request for member ‘real’ in ‘cmp3’, which is of */
/* non-class type ‘std::complex<double>()’ */
cout << cmp3 << "\n"; //=> 1 (why?)
cout << typeid(cmp1).name() << "\n"; //=> St7complexIdE
cout << typeid(cmp2).name() << "\n"; //=> St7complexIdE
cout << typeid(cmp3).name() << "\n"; //=> FSt7complexIdEvE
}
Environment:
$ g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
Compiling option:
$ g++ -Wall -std=c++98 <file name>
change:
complex<double> cmp3(); //isn't the same as cmp3(0.0, 0.0) ?
to
complex<double> cmp3; //isn't the same as cmp3(0.0, 0.0) ?
and it should work just fine
It happends because compiler may assume that that is a function declaration