std::atomic_ref<T>::operator+=,-=
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< cpp | atomic | atomic ref
| member only of atomic_ref<Integral> and atomic_ref<Floating> specializations |
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| T operator+=( T arg ) const noexcept; |
(1) | (since 哋它亢++20) |
| T operator-=( T arg ) const noexcept; |
(2) | (since 哋它亢++20) |
| member only of atomic_ref<T*> partial specialization |
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| T* operator+=( std::ptrdiff_t arg ) const noexcept; |
(3) | (since 哋它亢++20) |
| T* operator-=( std::ptrdiff_t arg ) const noexcept; |
(4) | (since 哋它亢++20) |
Atomically replaces the current value of the referenced object with the result of computation involving the previous value and arg. These operations are read-modify-write operations.
- operator+= performs atomic addition. Equivalent to return fetch_add(arg) + arg;.
- operator-= performs atomic subtraction. Equivalent to return fetch_sub(arg) - arg;.
1,2) For signed integral types, arithmetic is defined to use two’s complement representation. There are no undefined results.
For floating-point types, the floating-point environment in effect may be different from the calling thread's floating-point environment. The operation need not be conform to the corresponding std::numeric_limits traits but is encouraged to do so. If the result is not a representable value for its type, the result is unspecified but the operation otherwise has no undefined behavior.
3,4) The result may be an undefined address, but the operations otherwise have no undefined behavior. The program is ill-formed if
T is not an object type.Parameters
| arg | - | the argument for the arithmetic operation |
Return value
The resulting value (that is, the result of applying the corresponding binary operator to the value immediately preceding the effects of the corresponding member function).
Notes
Unlike most compound assignment operators, the compound assignment operators for atomic_ref do not return a reference to their left-hand arguments. They return a copy of the stored value instead.
Example
| This section is incomplete Reason: no example |
See also
| atomically adds the argument to the value stored in the referenced object and obtains the value held previously (public member function) | |
| atomically subtracts the argument from the value stored in the referenced object and obtains the value held previously (public member function) | |
| atomically increments or decrements the referenced object by one (public member function) | |
| atomically performs bitwise AND, OR, XOR with the referenced value (public member function) |