# std::experimental::promise (library fundamentals TS)

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This page is about the modified version of std::promise with type-erased allocator support provided by the Library Fundamentals TSes. For the version of `promise` provided by the concurrency TS supporting the `std::future` improvements made by that TS, see `std::experimental::concurrency_v1::promise`.

Defined in header `<experimental/future>` |  |
template< class R > class promise; | (1) | (library fundamentals TS)
template< class R > class promise<R&>; | (2) | (library fundamentals TS)
template<> class promise<void>; | (3) | (library fundamentals TS)

`std::experimental::fundamentals_v1::promise` (and `std::experimental::fundamentals_v2::promise`) is a modified version of std::promise provided by the library fundamentals TS with support for type-erased allocators.

### Member types

Member type | Definition
`allocator_type` | std::experimental::erased_type

### Member functions

(constructor) | constructs the promise object (public member function)
get_memory_resource | retrieves a pointer to the memory resource used by this object to allocate memory (public member function)

### Non-member function

std::experimental::swap(std::experimental::promise) | specializes the `swap` algorithm (function template)

### Helper classes

std::uses_allocator<std::experimental::promise> | specializes the std::uses_allocator type trait (class template specialization)

## Members identical to std::promise

### Member functions

(destructor) | destructs the promise object (public member function of `std::promise`)
operator= | assigns the shared state (public member function of `std::promise`)
swap | swaps two promise objects (public member function of `std::promise`)

##### Getting the result

get_future | returns a `future` associated with the promised result (public member function of `std::promise`)

##### Setting the result

set_value | sets the result to specific value (public member function of `std::promise`)
set_value_at_thread_exit | sets the result to specific value while delivering the notification only at thread exit (public member function of `std::promise`)
set_exception | sets the result to indicate an exception (public member function of `std::promise`)
set_exception_at_thread_exit | sets the result to indicate an exception while delivering the notification only at thread exit (public member function of `std::promise`)

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