487 lines
37 KiB
HTML
487 lines
37 KiB
HTML
<!DOCTYPE html>
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<title>std::basic_string<CharT,Traits,Allocator>::assign</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_assign skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_string<CharT,Traits,Allocator>::</span>assign</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-string.html">string</a>‎ | <a href="cpp-string-basic_string.html">basic string</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<td rowspan="142">(1)</td>
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> size_type count, CharT ch <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> size_type count, CharT ch <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(2)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(3)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx14">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br />
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size_type pos, size_type count <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx14">(C++14 前)</span></td>
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<tr class="t-dcl t-since-cxx14 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br />
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size_type pos, size_type count <span class="sy1">=</span> npos<span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> basic_string<span class="sy3">&</span> str,<br />
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size_type pos, size_type count <span class="sy1">=</span> npos<span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(4)</td>
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<tr class="t-dcl t-since-cxx11 t-until-cxx17">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> basic_string<span class="sy3">&&</span> str <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> basic_string<span class="sy3">&&</span> str <span class="br0">)</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> basic_string<span class="sy3">&&</span> str <span class="br0">)</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td rowspan="142">(5)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type count <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s, size_type count <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td></td>
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<td rowspan="142">(6)</td>
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<tr class="t-dcl t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> CharT<span class="sy2">*</span> s <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td></td>
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<td rowspan="142">(7)</td>
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<td></td>
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<tr class="t-dcl t-until-cxx20">
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<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> InputIt <span class="sy1">></span><br />
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basic_string<span class="sy3">&</span> assign<span class="br0">(</span> InputIt first, InputIt last <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<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> InputIt <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> InputIt first, InputIt last <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td rowspan="142">(8)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx11 t-until-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp">basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <a href="cpp-utility-initializer_list.html"><span class="kw960">std::<span class="me2">initializer_list</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span> ilist <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <a href="cpp-utility-initializer_list.html"><span class="kw960">std::<span class="me2">initializer_list</span></span></a><span class="sy1"><</span>CharT<span class="sy1">></span> ilist <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td rowspan="142">(9)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<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> T <span class="sy1">></span><br />
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basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<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> T <span class="sy1">></span><br />
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<span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tr>
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</tbody>
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<tbody></tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<tr class="t-dcl-rev-aux">
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<td></td>
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<td rowspan="142">(10)</td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-cxx17 t-until-cxx20">
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<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> T <span class="sy1">></span><br /></span>
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<p>basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos, size_type count <span class="sy1">=</span> npos<span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span><br />
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<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-cxx20">
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<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> T <span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</span> basic_string<span class="sy3">&</span> assign<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&</span> t,<br /></p>
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size_type pos, size_type count <span class="sy1">=</span> npos<span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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</tbody>
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<tbody>
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<tr class="t-dcl-sep">
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<p>替换字符串的内容。</p>
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<div class="t-li1"><span class="t-li">1)</span> 以 <code>count</code> 个 <code>ch</code> 的副本替换内容。</div>
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<div class="t-li1"><span class="t-li">2)</span> 以 <code>str</code> 的副本替换内容。等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this <span class="sy1">=</span> str<span class="sy4">;</span></span></span> 。<span class="t-rev-inl t-since-cxx11"><span>特别是可以发生分配器传播。</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span></div>
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<div class="t-li1"><span class="t-li">3)</span> 以 <code>str</code> 的子串 <code>[pos, pos+count)</code> 替换内容。若请求的子串越过 string 尾，或若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count <span class="sy1">==</span> npos</span></span> ，则产生的子串是 <code>[pos, str.size())</code> 。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">pos <span class="sy1">></span> str.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span></span></span> ，则抛出 <span class="t-lc"><a href="cpp-error-out_of_range.html">std::out_of_range</a></span> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> 用移动语义以 <code>str</code> 的内容替换内容。等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>str<span class="br0">)</span></span></span> 。特别是可以发生分配器传播。</div>
|
|
<div class="t-li1"><span class="t-li">5)</span> 以范围 <code>[s, s+count)</code> 中的字符的副本替换内容。此范围能含空字符。</div>
|
|
<div class="t-li1"><span class="t-li">6)</span> 以 <code>s</code> 所指向的空终止字符串的内容替换内容。由首个空字符，用 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">length</span><span class="br0">(</span>s<span class="br0">)</span></span></span> 确定字符串长度。</div>
|
|
<div class="t-li1"><span class="t-li">7)</span> 以范围 <code>[first, last)</code> 中的字符的副本替换内容。<span class="t-rev-inl t-since-cxx11"><span>若 <code>InputIt</code> 不满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> ，则此重载不参与重载决议。</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span></div>
|
|
<div class="t-li1"><span class="t-li">8)</span> 以 initializer_list <code>ilist</code> 的内容替换内容。</div>
|
|
<div class="t-li1"><span class="t-li">9)</span> 如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> 隐式转换 <code>t</code> 为 string_view <code>sv</code> ，然后以字符串视图 <code>sv</code> 的内容替换内容，如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp">assign<span class="br0">(</span>sv.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span>, sv.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span>。此重载仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 才参与重载决议。</div>
|
|
<div class="t-li1"><span class="t-li">10)</span> 如同用 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> sv <span class="sy1">=</span> t<span class="sy4">;</span></span></span> 隐式转换 <code>t</code> 为 string_view <code>sv</code> ，然后以来自 <code>sv</code> 的子视图 <code>[pos, pos+count)</code> 的字符替换内容。若请求的子视图越过 <code>sv</code> 的结尾，或若 <span class="t-c"><span class="mw-geshi cpp source-cpp">count <span class="sy1">==</span> npos</span></span> ，则产生的子视图为 <code>[pos, sv.size())</code> 。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">pos <span class="sy1">></span> sv.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span></span></span> ，则抛出 <span class="t-lc"><a href="cpp-error-out_of_range.html">std::out_of_range</a></span> 。此重载仅若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_convertible.html"><span class="kw593">std::<span class="me2">is_convertible_v</span></span></a><span class="sy1"><</span><span class="kw4">const</span> T<span class="sy3">&</span>, <span class="kw4">const</span> CharT<span class="sy2">*</span><span class="sy1">></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 才参与重载决议。</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>count</td>
|
|
<td>-</td>
|
|
<td>产生的 string 大小</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>pos</td>
|
|
<td>-</td>
|
|
<td>要取的首字符下标</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>ch</td>
|
|
<td>-</td>
|
|
<td>用以初始化字符串的字符的值</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>first, last</td>
|
|
<td>-</td>
|
|
<td>复制字符来源的范围</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>str</td>
|
|
<td>-</td>
|
|
<td>用作源以初始化字符的 string</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>s</td>
|
|
<td>-</td>
|
|
<td>指向用作源初始化 string 字符串的指针</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>ilist</td>
|
|
<td>-</td>
|
|
<td>用以初始化 string 字符的 <span class="t-lc"><a href="cpp-utility-initializer_list.html">std::initializer_list</a></span></td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>sv</td>
|
|
<td>-</td>
|
|
<td>用以初始化 string 字符的 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span></td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>t</td>
|
|
<td>-</td>
|
|
<td>用以初始化 string 字符的对象（可转换为 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> ）</td>
|
|
</tr>
|
|
<tr class="t-par-hitem">
|
|
<td colspan="3">类型要求</td>
|
|
</tr>
|
|
<tr class="t-par-req">
|
|
<td colspan="3">-
|
|
<div class="spacer"></div>
|
|
<code>InputIt</code> 必须满足<a href="cpp-named_req-InputIterator.html"><span style="font-style:italic">老式输入迭代器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(LegacyInputIterator)</span></a> 的要求。</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span></p>
|
|
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
|
|
<div class="t-li1"><span class="t-li">1)</span> 与 <code>count</code> 成线性</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 与 <code>str</code> 的大小成线性</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> 与 <code>count</code> 成线性</div>
|
|
<div class="t-li1"><span class="t-li">4)</span> 常数。若给定 <code>alloc</code> 且 <span class="t-c"><span class="mw-geshi cpp source-cpp">alloc <span class="sy3">!</span><span class="sy1">=</span> other.<span class="me1">get_allocator</span><span class="br0">(</span><span class="br0">)</span></span></span> ，则为线性。</div>
|
|
<div class="t-li1"><span class="t-li">5)</span> 与 <code>count</code> 成线性</div>
|
|
<div class="t-li1"><span class="t-li">6)</span> 与 <code>s</code> 的大小成线性</div>
|
|
<div class="t-li1"><span class="t-li">7)</span> 与 <code>first</code> 和 <code>last</code> 间的距离成线性</div>
|
|
<div class="t-li1"><span class="t-li">8)</span> 与 <code>ilist</code> 的大小成线性</div>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<p><span class="t-rev-inl t-since-cxx11"><span>若因任何原因抛出异常，则此函数无效果（强异常保证）。</span> <span><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></span></span></p>
|
|
<p>若操作会导致 <code>size() > max_size()</code> ，则抛出 <span class="t-lc"><a href="cpp-error-length_error.html">std::length_error</a></span> 。</p>
|
|
<table class="t-rev-begin">
|
|
<tr class="t-rev t-since-cxx17">
|
|
<td>
|
|
<div class="t-li1"><span class="t-li">4)</span>
|
|
<div class="t-noexcept-full"><a href="cpp-language-noexcept_spec.html"><tt>noexcept</tt></a> 规定：
|
|
<div class="t-noexcept-box"><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span><span class="br0">(</span><a href="cpp-memory-allocator_traits.html"><span class="kw701">std::<span class="me2">allocator_traits</span></span></a><span class="sy1"><</span>Allocator<span class="sy1">></span><span class="sy4">::</span><span class="me2">propagate_on_container_move_assignment</span><span class="sy4">::</span><span class="me2">value</span><br />
|
|
<span class="sy3">||</span> <a href="cpp-memory-allocator_traits.html"><span class="kw701">std::<span class="me2">allocator_traits</span></span></a><span class="sy1"><</span>Allocator<span class="sy1">></span><span class="sy4">::</span><span class="me2">is_always_equal</span><span class="sy4">::</span><span class="me2">value</span><span class="br0">)</span></span></span></div>
|
|
</div>
|
|
</div>
|
|
</td>
|
|
<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <iterator></span>
|
|
<span class="co2">#include <string></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> s<span class="sy4">;</span>
|
|
<span class="co1">// assign(size_type count, CharT ch)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><span class="nu0">4</span>, <span class="st0">'='</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "===="</span>
|
|
|
|
<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> <span class="kw4">const</span> c<span class="br0">(</span><span class="st0">"Exemplary"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="co1">// assign(basic_string const& str)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span>c<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> c <span class="sy1"><<</span> <span class="st0">"=="</span> <span class="sy1"><<</span> s <span class="sy1"><<</span><span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "Exemplary == Exemplary"</span>
|
|
|
|
<span class="co1">// assign(basic_string const& str, size_type pos, size_type count)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span>c, <span class="nu0">0</span>, c.<span class="me1">length</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "Exemplar";</span>
|
|
|
|
<span class="co1">// assign(basic_string&& str)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="br0">(</span><span class="st0">"C++ by "</span><span class="br0">)</span> <span class="sy2">+</span> <span class="st0">"example"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "C++ by example"</span>
|
|
|
|
<span class="co1">// assign(charT const* s, size_type count)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><span class="st0">"C-style string"</span>, <span class="nu0">7</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "C-style"</span>
|
|
|
|
<span class="co1">// assign(charT const* s)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><span class="st0">"C-style<span class="es5">\0</span>string"</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "C-style"</span>
|
|
|
|
<span class="kw4">char</span> mutable_c_str<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> <span class="st0">"C-style string"</span><span class="sy4">;</span>
|
|
<span class="co1">// assign(InputIt first, InputIt last)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><a href="cpp-iterator-begin.html"><span class="kw676">std::<span class="me2">begin</span></span></a><span class="br0">(</span>mutable_c_str<span class="br0">)</span>, <a href="cpp-iterator-end.html"><span class="kw680">std::<span class="me2">end</span></span></a><span class="br0">(</span>mutable_c_str<span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "C-style string"</span>
|
|
|
|
<span class="co1">// assign(std::initializer_list<charT> ilist)</span>
|
|
s.<span class="me1">assign</span><span class="br0">(</span><span class="br0">{</span> <span class="st0">'C'</span>, <span class="st0">'-'</span>, <span class="st0">'s'</span>, <span class="st0">'t'</span>, <span class="st0">'y'</span>, <span class="st0">'l'</span>, <span class="st0">'e'</span> <span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> s <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span> <span class="co1">// "C-style"</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">====
|
|
Exemplary==Exemplary
|
|
Exemplar
|
|
C++ by example
|
|
C-style
|
|
C-style
|
|
C-style string
|
|
C-style</pre></div>
|
|
</div>
|
|
</div>
|
|
<p><br /></p>
|
|
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
|
|
<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
|
|
<table class="dsctable" style="font-size:0.8em">
|
|
<tr>
|
|
<th>DR</th>
|
|
<th>应用于</th>
|
|
<th>出版时的行为</th>
|
|
<th>正确行为</th>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2063">LWG 2063</a></td>
|
|
<td>C++11</td>
|
|
<td>非标准化注释曾说交换是移动赋值的合法实现</td>
|
|
<td>更正为要求移动赋值</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2579">LWG 2579</a></td>
|
|
<td>C++11</td>
|
|
<td><code>assign(const basic_string&)</code> 不传播分配器</td>
|
|
<td>使之为若需要则传播分配器</td>
|
|
</tr>
|
|
<tr>
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<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2946">LWG 2946</a></td>
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<td>C++17</td>
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<td><code>string_view</code> 重载在某些情况下导致歧义</td>
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<td>通过使之为模板避免</td>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
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<div><a href="cpp-string-basic_string-basic_string.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
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</div>
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</td>
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<td>构造 <code>basic_string</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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</div>
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</td>
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<td>为字符串赋值<br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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