std::execution::read_env - cppreference.com (original) (raw)

| Defined in header | | | | -------------------------------------------------------------------------------- | | ------------------------------------------ | | inline constexpr /*unspecified*/ read_env{}; | | (since C++26) (customization point object) | | Call signature | | | | execution::sender auto read_env( auto&& query ); | | (since C++26) |

A sender factory that returns a sender that reaches into a receiver’s environment and pulls out the current value associated with a given query object.

For any query object q, the expression read_env(q) is expression-equivalent to /*make-sender*/(read_env, q).

Customization point objects

The name execution::read_env denotes a customization point object, which is a const function object of a literal semiregular class type. See CustomizationPointObject for details.

[edit] Example

An example usage of this factory is to schedule dependent work on the receiver's scheduler, which can be obtained with read_env(get_scheduler):

std::execution::sender auto task = std::execution::read_env(std::execution::get_scheduler) | std::execution::let_value([](auto sched) { return std::execution::starts_on(sched, /some nested work here/); });   std::this_thread::sync_wait( std::move(task) ); // wait for it to finish