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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="API documentation for the Rust `GraphemeCursor` struct in crate `unicode_segmentation`."><meta name="keywords" content="rust, rustlang, rust-lang, GraphemeCursor"><title>unicode_segmentation::GraphemeCursor - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="https://unicode-rs.github.io/unicode-rs_sm.png"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc struct"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">&#9776;</div><a href='../unicode_segmentation/index.html'><div class='logo-container'><img src='https://unicode-rs.github.io/unicode-rs_sm.png' alt='logo'></div></a><p class='location'>Struct GraphemeCursor</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.cur_cursor">cur_cursor</a><a href="#method.is_boundary">is_boundary</a><a href="#method.new">new</a><a href="#method.next_boundary">next_boundary</a><a href="#method.prev_boundary">prev_boundary</a><a href="#method.provide_context">provide_context</a><a href="#method.set_cursor">set_cursor</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Clone">Clone</a></div><a class="sidebar-title" href="#synthetic-implementations">Auto Trait Implementations</a><div class="sidebar-links"><a href="#impl-Send">Send</a><a href="#impl-Sync">Sync</a><a href="#impl-Unpin">Unpin</a></div><a class="sidebar-title" href="#blanket-implementations">Blanket Implementations</a><div class="sidebar-links"><a href="#impl-Any">Any</a><a href="#impl-Borrow%3CT%3E">Borrow&lt;T&gt;</a><a href="#impl-BorrowMut%3CT%3E">BorrowMut&lt;T&gt;</a><a href="#impl-From%3CT%3E">From&lt;T&gt;</a><a href="#impl-Into%3CU%3E">Into&lt;U&gt;</a><a href="#impl-TryFrom%3CU%3E">TryFrom&lt;U&gt;</a><a href="#impl-TryInto%3CU%3E">TryInto&lt;U&gt;</a></div></div><p class='location'><a href='index.html'>unicode_segmentation</a></p><script>window.sidebarCurrent = {name: 'GraphemeCursor', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press S to search, ? for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>&#x2212;</span>]</a></span><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#157-181' title='goto source code'>[src]</a></span><span class='in-band'>Struct <a href='index.html'>unicode_segmentation</a>::<wbr><a class="struct" href=''>GraphemeCursor</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><pre class='rust struct'>pub struct GraphemeCursor { /* fields omitted */ }</pre></div><div class='docblock'><p>Cursor-based segmenter for grapheme clusters.</p>
</div><h2 id='methods' class='small-section-header'>Methods<a href='#methods' class='anchor'></a></h2><h3 id='impl' class='impl'><code class='in-band'>impl <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a href='#impl' class='anchor'></a><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#252-670' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.new' class="method"><code id='new.v'>pub fn <a href='#method.new' class='fnname'>new</a>(offset: usize, len: usize, is_extended: bool) -&gt; <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#267-284' title='goto source code'>[src]</a></h4><div class='docblock'><p>Create a new cursor. The string and initial offset are given at creation
time, but the contents of the string are not. The <code>is_extended</code> parameter
controls whether extended grapheme clusters are selected.</p>
<p>The <code>offset</code> parameter must be on a codepoint boundary.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">&quot;हिन्दी&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">legacy</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">0</span>, <span class="ident">s</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">legacy</span>.<span class="ident">next_boundary</span>(<span class="ident">s</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="string">&quot;&quot;</span>.<span class="ident">len</span>())));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">extended</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">0</span>, <span class="ident">s</span>.<span class="ident">len</span>(), <span class="bool-val">true</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">extended</span>.<span class="ident">next_boundary</span>(<span class="ident">s</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="string">&quot;हि&quot;</span>.<span class="ident">len</span>())));</pre></div>
</div><h4 id='method.set_cursor' class="method"><code id='set_cursor.v'>pub fn <a href='#method.set_cursor' class='fnname'>set_cursor</a>(&amp;mut self, offset: usize)</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#298-311' title='goto source code'>[src]</a></h4><div class='docblock'><p>Set the cursor to a new location in the same string.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">&quot;abcd&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">0</span>, <span class="ident">s</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">cur_cursor</span>(), <span class="number">0</span>);
<span class="ident">cursor</span>.<span class="ident">set_cursor</span>(<span class="number">2</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">cur_cursor</span>(), <span class="number">2</span>);</pre></div>
</div><h4 id='method.cur_cursor' class="method"><code id='cur_cursor.v'>pub fn <a href='#method.cur_cursor' class='fnname'>cur_cursor</a>(&amp;self) -&gt; usize</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#326-328' title='goto source code'>[src]</a></h4><div class='docblock'><p>The current offset of the cursor. Equal to the last value provided to
<code>new()</code> or <code>set_cursor()</code>, or returned from <code>next_boundary()</code> or
<code>prev_boundary()</code>.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="comment">// Two flags (🇷🇸🇮🇴), each flag is two RIS codepoints, each RIS is 4 bytes.</span>
<span class="kw">let</span> <span class="ident">flags</span> <span class="op">=</span> <span class="string">&quot;\u{1F1F7}\u{1F1F8}\u{1F1EE}\u{1F1F4}&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">4</span>, <span class="ident">flags</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">cur_cursor</span>(), <span class="number">4</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">8</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">cur_cursor</span>(), <span class="number">8</span>);</pre></div>
</div><h4 id='method.provide_context' class="method"><code id='provide_context.v'>pub fn <a href='#method.provide_context' class='fnname'>provide_context</a>(&amp;mut self, chunk: &amp;str, chunk_start: usize)</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#349-368' title='goto source code'>[src]</a></h4><div class='docblock'><p>Provide additional pre-context when it is needed to decide a boundary.
The end of the chunk must coincide with the value given in the
<code>GraphemeIncomplete::PreContext</code> request.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">flags</span> <span class="op">=</span> <span class="string">&quot;\u{1F1F7}\u{1F1F8}\u{1F1EE}\u{1F1F4}&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">8</span>, <span class="ident">flags</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="comment">// Not enough pre-context to decide if there&#39;s a boundary between the two flags.</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">is_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">flags</span>[<span class="number">8</span>..], <span class="number">8</span>), <span class="prelude-val">Err</span>(<span class="ident">GraphemeIncomplete</span>::<span class="ident">PreContext</span>(<span class="number">8</span>)));
<span class="comment">// Provide one more Regional Indicator Symbol of pre-context</span>
<span class="ident">cursor</span>.<span class="ident">provide_context</span>(<span class="kw-2">&amp;</span><span class="ident">flags</span>[<span class="number">4</span>..<span class="number">8</span>], <span class="number">4</span>);
<span class="comment">// Still not enough context to decide.</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">is_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">flags</span>[<span class="number">8</span>..], <span class="number">8</span>), <span class="prelude-val">Err</span>(<span class="ident">GraphemeIncomplete</span>::<span class="ident">PreContext</span>(<span class="number">4</span>)));
<span class="comment">// Provide additional requested context.</span>
<span class="ident">cursor</span>.<span class="ident">provide_context</span>(<span class="kw-2">&amp;</span><span class="ident">flags</span>[<span class="number">0</span>..<span class="number">4</span>], <span class="number">0</span>);
<span class="comment">// That&#39;s enough to decide (it always is when context goes to the start of the string)</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">is_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">flags</span>[<span class="number">8</span>..], <span class="number">8</span>), <span class="prelude-val">Ok</span>(<span class="bool-val">true</span>));</pre></div>
</div><h4 id='method.is_boundary' class="method"><code id='is_boundary.v'>pub fn <a href='#method.is_boundary' class='fnname'>is_boundary</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk: &amp;str, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk_start: usize<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;bool, <a class="enum" href="../unicode_segmentation/enum.GraphemeIncomplete.html" title="enum unicode_segmentation::GraphemeIncomplete">GraphemeIncomplete</a>&gt;</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#461-517' title='goto source code'>[src]</a></h4><div class='docblock'><p>Determine whether the current cursor location is a grapheme cluster boundary.
Only a part of the string need be supplied. If <code>chunk_start</code> is nonzero or
the length of <code>chunk</code> is not equal to <code>len</code> on creation, then this method
may return <code>GraphemeIncomplete::PreContext</code>. The caller should then
call <code>provide_context</code> with the requested chunk, then retry calling this
method.</p>
<p>For partial chunks, if the cursor is not at the beginning or end of the
string, the chunk should contain at least the codepoint following the cursor.
If the string is nonempty, the chunk must be nonempty.</p>
<p>All calls should have consistent chunk contents (ie, if a chunk provides
content for a given slice, all further chunks covering that slice must have
the same content for it).</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">flags</span> <span class="op">=</span> <span class="string">&quot;\u{1F1F7}\u{1F1F8}\u{1F1EE}\u{1F1F4}&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">8</span>, <span class="ident">flags</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">is_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="bool-val">true</span>));
<span class="ident">cursor</span>.<span class="ident">set_cursor</span>(<span class="number">12</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">is_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="bool-val">false</span>));</pre></div>
</div><h4 id='method.next_boundary' class="method"><code id='next_boundary.v'>pub fn <a href='#method.next_boundary' class='fnname'>next_boundary</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk: &amp;str, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk_start: usize<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;usize&gt;, <a class="enum" href="../unicode_segmentation/enum.GraphemeIncomplete.html" title="enum unicode_segmentation::GraphemeIncomplete">GraphemeIncomplete</a>&gt;</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#551-592' title='goto source code'>[src]</a></h4><div class='docblock'><p>Find the next boundary after the current cursor position. Only a part of
the string need be supplied. If the chunk is incomplete, then this
method might return <code>GraphemeIncomplete::PreContext</code> or
<code>GraphemeIncomplete::NextChunk</code>. In the former case, the caller should
call <code>provide_context</code> with the requested chunk, then retry. In the
latter case, the caller should provide the chunk following the one
given, then retry.</p>
<p>See <code>is_boundary</code> for expectations on the provided chunk.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">flags</span> <span class="op">=</span> <span class="string">&quot;\u{1F1F7}\u{1F1F8}\u{1F1EE}\u{1F1F4}&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">4</span>, <span class="ident">flags</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">8</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">16</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>));</pre></div>
<p>And an example that uses partial strings:</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">&quot;abcd&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">0</span>, <span class="ident">s</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">1</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Err</span>(<span class="ident">GraphemeIncomplete</span>::<span class="ident">NextChunk</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">3</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">4</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">next_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>));</pre></div>
</div><h4 id='method.prev_boundary' class="method"><code id='prev_boundary.v'>pub fn <a href='#method.prev_boundary' class='fnname'>prev_boundary</a>(<br>&nbsp;&nbsp;&nbsp;&nbsp;&amp;mut self, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk: &amp;str, <br>&nbsp;&nbsp;&nbsp;&nbsp;chunk_start: usize<br>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="enum" href="https://doc.rust-lang.org/nightly/core/option/enum.Option.html" title="enum core::option::Option">Option</a>&lt;usize&gt;, <a class="enum" href="../unicode_segmentation/enum.GraphemeIncomplete.html" title="enum unicode_segmentation::GraphemeIncomplete">GraphemeIncomplete</a>&gt;</code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#627-669' title='goto source code'>[src]</a></h4><div class='docblock'><p>Find the previous boundary after the current cursor position. Only a part
of the string need be supplied. If the chunk is incomplete, then this
method might return <code>GraphemeIncomplete::PreContext</code> or
<code>GraphemeIncomplete::PrevChunk</code>. In the former case, the caller should
call <code>provide_context</code> with the requested chunk, then retry. In the
latter case, the caller should provide the chunk preceding the one
given, then retry.</p>
<p>See <code>is_boundary</code> for expectations on the provided chunk.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">flags</span> <span class="op">=</span> <span class="string">&quot;\u{1F1F7}\u{1F1F8}\u{1F1EE}\u{1F1F4}&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">12</span>, <span class="ident">flags</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">8</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">0</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="ident">flags</span>, <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>));</pre></div>
<p>And an example that uses partial strings (note the exact return is not
guaranteed, and may be <code>PrevChunk</code> or <code>PreContext</code> arbitrarily):</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">&quot;abcd&quot;</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">cursor</span> <span class="op">=</span> <span class="ident">GraphemeCursor</span>::<span class="ident">new</span>(<span class="number">4</span>, <span class="ident">s</span>.<span class="ident">len</span>(), <span class="bool-val">false</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">3</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">2</span>..<span class="number">4</span>], <span class="number">2</span>), <span class="prelude-val">Err</span>(<span class="ident">GraphemeIncomplete</span>::<span class="ident">PrevChunk</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">0</span>..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">2</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">0</span>..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">1</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">0</span>..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(<span class="number">0</span>)));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">cursor</span>.<span class="ident">prev_boundary</span>(<span class="kw-2">&amp;</span><span class="ident">s</span>[<span class="number">0</span>..<span class="number">2</span>], <span class="number">0</span>), <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>));</pre></div>
</div></div><h2 id='implementations' class='small-section-header'>Trait Implementations<a href='#implementations' class='anchor'></a></h2><div id='implementations-list'><h3 id='impl-Clone' class='impl'><code class='in-band'>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html" title="trait core::clone::Clone">Clone</a> for <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a href='#impl-Clone' class='anchor'></a><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#156' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.clone' class="method hidden"><code id='clone.v'>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&amp;self) -&gt; <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a class='srclink' href='../src/unicode_segmentation/grapheme.rs.html#156' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Returns a copy of the value. <a href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
</div><h4 id='method.clone_from' class="method hidden"><code id='clone_from.v'>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&amp;mut self, source: &amp;Self)</code><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/clone.rs.html#131-133' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Performs copy-assignment from <code>source</code>. <a href="https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from">Read more</a></p>
</div></div></div><h2 id='synthetic-implementations' class='small-section-header'>Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a></h2><div id='synthetic-implementations-list'><h3 id='impl-Send' class='impl'><code class='in-band'>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a href='#impl-Send' class='anchor'></a></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><code class='in-band'>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a href='#impl-Sync' class='anchor'></a></h3><div class='impl-items'></div><h3 id='impl-Unpin' class='impl'><code class='in-band'>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a> for <a class="struct" href="../unicode_segmentation/struct.GraphemeCursor.html" title="struct unicode_segmentation::GraphemeCursor">GraphemeCursor</a></code><a href='#impl-Unpin' class='anchor'></a></h3><div class='impl-items'></div></div><h2 id='blanket-implementations' class='small-section-header'>Blanket Implementations<a href='#blanket-implementations' class='anchor'></a></h2><div id='blanket-implementations-list'><h3 id='impl-From%3CT%3E' class='impl'><code class='in-band'>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt; for T</code><a href='#impl-From%3CT%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#552-554' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.from' class="method hidden"><code id='from.v'>fn <a href='https://doc.rust-lang.org/nightly/core/convert/trait.From.html#tymethod.from' class='fnname'>from</a>(t: T) -&gt; T</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#553' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Performs the conversion.</p>
</div></div><h3 id='impl-TryFrom%3CU%3E' class='impl'><code class='in-band'>impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;T&gt;,&nbsp;</span></code><a href='#impl-TryFrom%3CU%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#571-577' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='associatedtype.Error' class="type"><code id='Error.t'>type <a href='https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html#associatedtype.Error' class="type">Error</a> = <a class="enum" href="https://doc.rust-lang.org/nightly/core/convert/enum.Infallible.html" title="enum core::convert::Infallible">Infallible</a></code></h4><div class='docblock'><p>The type returned in the event of a conversion error.</p>
</div><h4 id='method.try_from' class="method hidden"><code id='try_from.v'>fn <a href='https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html#tymethod.try_from' class='fnname'>try_from</a>(value: U) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;T, &lt;T as <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;U&gt;&gt;::<a class="type" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#574-576' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Performs the conversion.</p>
</div></div><h3 id='impl-Into%3CU%3E' class='impl'><code class='in-band'>impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.Into.html" title="trait core::convert::Into">Into</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.From.html" title="trait core::convert::From">From</a>&lt;T&gt;,&nbsp;</span></code><a href='#impl-Into%3CU%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#543-548' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.into' class="method hidden"><code id='into.v'>fn <a href='https://doc.rust-lang.org/nightly/core/convert/trait.Into.html#tymethod.into' class='fnname'>into</a>(self) -&gt; U</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#545-547' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Performs the conversion.</p>
</div></div><h3 id='impl-TryInto%3CU%3E' class='impl'><code class='in-band'>impl&lt;T, U&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryInto.html" title="trait core::convert::TryInto">TryInto</a>&lt;U&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;U: <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;,&nbsp;</span></code><a href='#impl-TryInto%3CU%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#559-566' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='associatedtype.Error-1' class="type"><code id='Error.t-1'>type <a href='https://doc.rust-lang.org/nightly/core/convert/trait.TryInto.html#associatedtype.Error' class="type">Error</a> = &lt;U as <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="type" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a></code></h4><div class='docblock'><p>The type returned in the event of a conversion error.</p>
</div><h4 id='method.try_into' class="method hidden"><code id='try_into.v'>fn <a href='https://doc.rust-lang.org/nightly/core/convert/trait.TryInto.html#tymethod.try_into' class='fnname'>try_into</a>(self) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;U, &lt;U as <a class="trait" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html" title="trait core::convert::TryFrom">TryFrom</a>&lt;T&gt;&gt;::<a class="type" href="https://doc.rust-lang.org/nightly/core/convert/trait.TryFrom.html#associatedtype.Error" title="type core::convert::TryFrom::Error">Error</a>&gt;</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/convert.rs.html#563-565' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Performs the conversion.</p>
</div></div><h3 id='impl-Borrow%3CT%3E' class='impl'><code class='in-band'>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/borrow/trait.Borrow.html" title="trait core::borrow::Borrow">Borrow</a>&lt;T&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></code><a href='#impl-Borrow%3CT%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/borrow.rs.html#213-215' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.borrow' class="method hidden"><code id='borrow.v'>fn <a href='https://doc.rust-lang.org/nightly/core/borrow/trait.Borrow.html#tymethod.borrow' class='fnname'>borrow</a>(&amp;self) -&gt; &amp;T</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/borrow.rs.html#214' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Immutably borrows from an owned value. <a href="https://doc.rust-lang.org/nightly/core/borrow/trait.Borrow.html#tymethod.borrow">Read more</a></p>
</div></div><h3 id='impl-BorrowMut%3CT%3E' class='impl'><code class='in-band'>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/borrow/trait.BorrowMut.html" title="trait core::borrow::BorrowMut">BorrowMut</a>&lt;T&gt; for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></code><a href='#impl-BorrowMut%3CT%3E' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/borrow.rs.html#218-220' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.borrow_mut' class="method hidden"><code id='borrow_mut.v'>fn <a href='https://doc.rust-lang.org/nightly/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut' class='fnname'>borrow_mut</a>(&amp;mut self) -&gt; &amp;mut T</code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/borrow.rs.html#219' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Mutably borrows from an owned value. <a href="https://doc.rust-lang.org/nightly/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut">Read more</a></p>
</div></div><h3 id='impl-Any' class='impl'><code class='in-band'>impl&lt;T&gt; <a class="trait" href="https://doc.rust-lang.org/nightly/core/any/trait.Any.html" title="trait core::any::Any">Any</a> for T <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;T: 'static + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,&nbsp;</span></code><a href='#impl-Any' class='anchor'></a><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/any.rs.html#100-102' title='goto source code'>[src]</a></h3><div class='impl-items'><h4 id='method.type_id' class="method hidden"><code id='type_id.v'>fn <a href='https://doc.rust-lang.org/nightly/core/any/trait.Any.html#tymethod.type_id' class='fnname'>type_id</a>(&amp;self) -&gt; <a class="struct" href="https://doc.rust-lang.org/nightly/core/any/struct.TypeId.html" title="struct core::any::TypeId">TypeId</a></code><a class='srclink' href='https://doc.rust-lang.org/nightly/src/core/any.rs.html#101' title='goto source code'>[src]</a></h4><div class='docblock hidden'><p>Gets the <code>TypeId</code> of <code>self</code>. <a href="https://doc.rust-lang.org/nightly/core/any/trait.Any.html#tymethod.type_id">Read more</a></p>
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