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std::optional<T>::
operator bool,
std::optional<T>::
has_value
From cppreference.com
<
cpp
|
utility
|
optional
C++
Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros
(C++20)
Language support library
Concepts library
(C++20)
Diagnostics library
Memory management library
Metaprogramming library
(C++11)
General utilities library
Containers library
Iterators library
Ranges library
(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library
(C++17)
Concurrency support library
(C++11)
Execution control library
(C++26)
Technical specifications
Symbols index
External libraries
[edit]
Utilities library
Language support
Type support
(basic types, RTTI)
Library feature-test macros
(C++20)
Program utilities
Variadic functions
initializer_list
(C++11)
is_constant_evaluated
(C++20)
is_within_lifetime
(C++26)
source_location
(C++20)
Coroutine support
(C++20)
Contract support
(C++26)
Three-way comparison
three_way_comparable
three_way_comparable_with
(C++20)
(C++20)
strong_ordering
(C++20)
weak_ordering
(C++20)
partial_ordering
(C++20)
common_comparison_category
(C++20)
compare_three_way_result
(C++20)
compare_three_way
(C++20)
strong_order
(C++20)
weak_order
(C++20)
partial_order
(C++20)
compare_strong_order_fallback
(C++20)
compare_weak_order_fallback
(C++20)
compare_partial_order_fallback
(C++20)
is_eq
is_lt
is_lteq
(C++20)
(C++20)
(C++20)
is_neq
is_gt
is_gteq
(C++20)
(C++20)
(C++20)
General utilities
Function objects
Bit manipulation
(C++20)
C-style bit manipulation
(C++26)
bitset
hash
(C++11)
Relational operators
(deprecated in C++20)
rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Integer comparison functions
cmp_equal
cmp_less
cmp_less_than
(C++20)
(C++20)
(C++20)