tmp/tmp822pjyi_/{from.md → to.md}
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| 1 |
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### Class template `prop` <a id="exec.prop">[[exec.prop]]</a>
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``` cpp
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namespace std::execution {
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template<class QueryTag, class ValueType>
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struct prop {
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QueryTag query_; // exposition only
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ValueType value_; // exposition only
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constexpr const ValueType& query(QueryTag) const noexcept {
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return value_;
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}
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};
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template<class QueryTag, class ValueType>
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prop(QueryTag, ValueType) -> prop<QueryTag, unwrap_reference_t<ValueType>>;
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}
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```
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Class template `prop` is for building a queryable object from a query
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object and a value.
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*Mandates:* `callable<QueryTag, prop-like<ValueType>>` is modeled, where
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*`prop-like`* is the following exposition-only class template:
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``` cpp
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template<class ValueType>
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struct prop-like { // exposition only
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const ValueType& query(auto) const noexcept;
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};
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```
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[*Example 1*:
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``` cpp
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template<sender Sndr>
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sender auto parameterize_work(Sndr sndr) {
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// Make an environment such that get_allocator(env) returns a reference to a copy of my_alloc{}.
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auto e = prop(get_allocator, my_alloc{});
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// Parameterize the input sender so that it will use our custom execution environment.
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return write_env(sndr, e);
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}
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```
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— *end example*]
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Specializations of `prop` are not assignable.
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