std::literals::complex_literals::operator""i,operator""if,operator""il(3)

NAME
std::literals::complex_literals::operator""i,operator""if,operator""il - std::literals::complex_literals::operator""i,operator""if,operator""il

Synopsis
   Defined in header <complex>
   constexpr complex< double > operator""i( long double arg ); (1) (since C++14)
   constexpr complex< double > operator""i( unsigned long long arg );
   constexpr complex< float > operator""if( long double arg ); (2) (since C++14)
   constexpr complex< float > operator""if( unsigned long long arg );
   constexpr complex< long double > operator""il( long double arg );
   constexpr complex< long double > operator""il( unsigned long long (3) (since C++14)
   arg );
   Forms a std::complex literal representing an imaginary number.
   1) forms a literal std::complex<double> with the real part zero and imaginary part
   arg
   2) forms a literal std::complex<float> with the real part zero and imaginary part
   arg
   3) forms a literal std::complex<long double> with the real part zero and imaginary
   part arg

Parameters
   arg - the value of the imaginary number

Return value
   The std::complex literal with the real part zero and imaginary part arg

Notes
   These operators are declared in the namespace std::literals::complex_literals, where
   both literals and complex_literals are inline namespaces. Access to these operators
   can be gained with using namespace std::literals, using namespace
   std::complex_literals, and using namespace std::literals::complex_literals.
   Even though if is a keyword in C++, it is a ud-suffix of the literal operator of the
   form operator ""if and in the literal expressions such as 1if or 1.0if because it is
   not separated by whitespace and is not a standalone token.
   Feature-test macro: __cpp_lib_complex_udls

Possible implementation

First version
   constexpr std::complex<double> operator""i(unsigned long long d)
   {
       return std::complex<double>{0.0, static_cast<double>(d)};
   }
   constexpr std::complex<double> operator""i(long double d)
   {
       return std::complex<double>{0.0, static_cast<double>(d)};
   }

Second version
   constexpr std::complex<float> operator""if(unsigned long long d)
   {
       return std::complex<float>{0.0f, static_cast<float>(d)};
   }
   constexpr std::complex<float> operator""if(long double d)
   {
       return std::complex<float>{0.0f, static_cast<float>(d)};
   }
                        Third version
   constexpr std::complex<long double> operator""il(unsigned long long d)
   {
       return std::complex<long double>{0.0L, static_cast<long double>(d)};
   }
   constexpr std::complex<long double> operator""il(long double d)
   {
       return std::complex<long double>{0.0L, d};
   }

Example

// Run this code
 #include <iostream>
 #include <complex>
 int main()
 {
     using namespace std::complex_literals;
     std::complex<double> c = 1.0 + 1i;
     std::cout << "abs" << c << " = " << std::abs(c) << '\n';
     std::complex<float> z = 3.0f + 4.0if;
     std::cout << "abs" << z << " = " << std::abs(z) << '\n';
 }

Output:
 abs(1,1) = 1.41421
 abs(3,4) = 5

See also
   constructor constructs a complex number
                 (public member function)
   operator= assigns the contents
                 (public member function)