115 lines
9.7 KiB
HTML
115 lines
9.7 KiB
HTML
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<title>std::experimental::promise<R>::promise (库基础 TS)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::experimental::promise<R>::</span>promise <span class="t-mark-rev t-since-libfund-ts t-mark-ts">(库基础 TS)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-experimental.html">experimental</a>‎ | <a href="cpp-experimental-lib_extensions.html">lib extensions</a>‎ | <a href="cpp-experimental-lib_extensions-promise.html">promise</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-libfund-ts t-mark-ts">(库基础 TS)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Alloc <span class="sy1">></span><br />
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promise<span class="br0">(</span> <a href="cpp-memory-allocator_arg_t.html"><span class="kw702">std::<span class="me2">allocator_arg_t</span></span></a>, <span class="kw4">const</span> Alloc<span class="sy3">&</span> alloc <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-libfund-ts t-mark-ts">(库基础 TS)</span></td>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span> promise<span class="sy3">&&</span> other <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-libfund-ts t-mark-ts">(库基础 TS)</span></td>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span> <span class="kw4">const</span> promise<span class="sy3">&</span> other <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-libfund-ts t-mark-ts">(库基础 TS)</span></td>
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<td></td>
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<td></td>
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<td></td>
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<p>构造 <code>std::experimental::promise</code> 对象。</p>
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<div class="t-li1"><span class="t-li">1)</span> 默认构造函数。构造拥有空共享状态的 <code>promise</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 构造拥有空共享状态的 <code>promise</code> 。用被当做类型擦除分配器（见后述）的 <code>alloc</code> 分配共享状态。</div>
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<div class="t-li1"><span class="t-li">3)</span> 移动构造函数。用移动语义构造拥有 <code>other</code> 的共享状态的 <code>promise</code> 。构造后， <code>other</code> 无共享状态。</div>
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<div class="t-li1"><span class="t-li">4)</span> <code>std::experimental::promise</code> 不可复制。</div>
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<h3><span class="mw-headline" id=".E7.B1.BB.E5.9E.8B.E6.93.A6.E9.99.A4.E7.9A.84.E5.88.86.E9.85.8D.E5.99.A8">类型擦除的分配器</span></h3>
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<p><code>promise</code> 的接收分配器参数 <code>alloc</code> 的构造函数将参数当做类型擦除的分配器。以分配器参数（若指定）确定 <code>promise</code> 用来分配内存的 memory_resource 指针，如下：</p>
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<td><code>alloc</code> 的类型</td>
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<td>memory_resource 指针的值</td>
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<td>不存在（构造时不指定分配器）</td>
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<td>构造时 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="http://zh.cppreference.com/w/cpp/experimental/get_default_resource"><span class="kw2312">std::<span class="me2">experimental</span><span class="sy4">::</span><span class="me2">pmr</span><span class="sy4">::</span><span class="me2">get_default_resource</span></span></a><span class="br0">(</span><span class="br0">)</span></span></span> 的值。</td>
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<td><span class="t-lc"><a href="cpp-types-nullptr_t.html">std::nullptr_t</a></span></td>
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<td>构造时 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="http://zh.cppreference.com/w/cpp/experimental/get_default_resource"><span class="kw2312">std::<span class="me2">experimental</span><span class="sy4">::</span><span class="me2">pmr</span><span class="sy4">::</span><span class="me2">get_default_resource</span></span></a><span class="br0">(</span><span class="br0">)</span></span></span> 的值。</td>
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<td>可转换为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="http://zh.cppreference.com/w/cpp/experimental/memory_resource"><span class="kw2304">std::<span class="me2">experimental</span><span class="sy4">::</span><span class="me2">pmr</span><span class="sy4">::</span><span class="me2">memory_resource</span></span></a><span class="sy2">*</span></span></span><br />
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的指针类型</td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1"><</span><a href="http://zh.cppreference.com/w/cpp/experimental/memory_resource"><span class="kw2304">std::<span class="me2">experimental</span><span class="sy4">::</span><span class="me2">pmr</span><span class="sy4">::</span><span class="me2">memory_resource</span></span></a><span class="sy2">*</span><span class="sy1">></span><span class="br0">(</span>alloc<span class="br0">)</span></span></span></td>
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<td><span class="t-lc"><a href="https://zh.cppreference.com/mwiki/index.php?title=cpp/experimental/polymorphic_allocator&action=edit&redlink=1" class="new" title="cpp/experimental/polymorphic allocator（页面不存在）">std::experimental::pmr::polymorphic_allocator</a></span><br />
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的特化</td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">alloc.<span class="me1">resource</span><span class="br0">(</span><span class="br0">)</span></span></span></td>
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<td>任何其他符合<a href="cpp-named_req-Allocator.html"><span style="font-style:italic">分配器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Allocator)</span></a> 要求的类型</td>
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<td>指向 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-experimental-resource_adaptor.html"><span class="kw2309">std::<span class="me2">experimental</span><span class="sy4">::</span><span class="me2">pmr</span><span class="sy4">::</span><span class="me2">resource_adaptor</span></span></a><span class="sy1"><</span>A<span class="sy1">></span><span class="br0">(</span>alloc<span class="br0">)</span></span></span> 类型对象的指针，其中 <code>A</code> 是 <code>alloc</code> 的类型。指针仅在 <code>promise</code> 对象的生存期内保持合法。</td>
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<td>非以上类型</td>
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<td>程序为病式</td>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>alloc</td>
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<td>-</td>
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<td>用于分配共享状态的分配器</td>
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<tr class="t-par">
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<td>other</td>
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<td>-</td>
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<td>取得其共享状态的另一 <code>std::experimental::promise</code></td>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<div class="t-li1"><span class="t-li">1-2)</span> （无）</div>
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<div class="visualClear"></div>
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