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template
<class
CharType,
class CharTrait, class T>
std::basic_ostream<CharType, CharTrait>& [br]
operator<<(std::basic_ostream<CharType, CharTrait>&
out,
optional<T> const& v);
v
contains a value, the output contains result of calling out <<
*v.
out.
template <class CharType, class CharTrait,
class T>
std::basic_ostream<CharType,
CharTrait>& [br] operator<<(std::basic_ostream<CharType, CharTrait>& out, none_t);
out.
template <class CharType, class CharTrait,
class T>
std::basic_ostream<CharType,
CharTrait>& [br] operator>>(std::basic_istream<CharType, CharTrait>& in, optional<T>& v);
T
is DefaultConstructible and
MoveConstructible.
in. If
the string representation indicates that the optional object should
contain a value, v
contains a value and its contained value is obtained as if by default-constructing
an object o of type
T and then calling
in >>
o; otherwise v does not contain a value, and the
previously contained value (if any) has been destroyed.
out.