From cppreference.com
< cpp‎ | numeric‎ | complex
Defined in header <complex>
template <class T, class CharT, class Traits>

std::basic_ostream<CharT, Traits>&
    operator<<(std::basic_ostream<CharT, Traits>& os,

               const std::complex<T>& x);
template <class T, class CharT, class Traits>

std::basic_istream<CharT, Traits>&
    operator>>(std::basic_istream<CharT, Traits>& is,

               std::complex<T>& x);
1) Writes to os the complex number in the form (real,imaginary).
2) Reads a complex number from is. The supported formats are
  • real
  • (real)
  • (real,imaginary)

Where the input for real and imaginary must be convertible to T.

If an error occurs calls is.setstate(ios_base::failbit)


[edit] Exceptions

May throw std::ios_base::failure on stream errors.

[edit] Parameters

os - a character output stream
is - a character input stream
x - the complex number to be inserted or extracted

[edit] Return value

1) os
2) is

[edit] Notes

1) As the comma may be used in the current locale as decimal separator, the output may be ambiguous. This can be solved with std::showpoint which forces the decimal separator to be visible.
2) The input is performed as a series of simple formatted extractions. Whitespace skipping is the same for each of them.

[edit] Possible implementation

template<class T, class charT, class traits>
basic_ostream<charT, traits>& 
operator<<(basic_ostream<charT, traits>& o, const complex<T>& x) {
    basic_ostringstream<charT, traits> s;
    s <<(<< x.real() << "," << x.imag() <<);
    return o << s.str();