std::nullopt

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Compiler support
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Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Diagnostics library
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Metaprogramming library (C++11)
General utilities library
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Execution control library (C++26)
Technical specifications
Symbols index
External libraries

Member functions
optional::optional
optional::~optional
optional::operator=
Observers
optional::operator->optional::operator*
optional::operator booloptional::has_value
optional::value
optional::value_or
Iterators
optional::begin (C++26)
optional::end (C++26)
Monadic operations
optional::and_then (C++23)
optional::transform (C++23)
optional::or_else (C++23)
Modifiers
optional::emplace
optional::swap
optional::reset
Non-member functions
operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20)
make_optional
swap(std::optional)
Deduction guides
Helper classes
hash<std::optional>
nullopt_t
in_place_t