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<p class='location'><a href='index.html'>either</a></p><script>window.sidebarCurrent = {name: 'try_left', ty: 'macro', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>either</a>::<wbr><a class="macro" href=''>try_left</a></span><span class='out-of-band'><span id='render-detail'>
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<pre class="rust macro">
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<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">try_left</span> {
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">expr</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
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}</pre>
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<div class='docblock'><p>Macro for unwrapping the left side of an <code>Either</code>, which fails early
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with the opposite side. Can only be used in functions that return
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<code>Either</code> because of the early return of <code>Right</code> that it provides.</p>
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<p>See also <code>try_right!</code> for its dual, which applies the same just to the
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right side.</p>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<pre class="rust rust-example-rendered">
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<span class="attribute">#[<span class="ident">macro_use</span>]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">either</span>;
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<span class="kw">use</span> <span class="ident">either</span>::{<span class="ident">Either</span>, <span class="ident">Left</span>, <span class="ident">Right</span>};
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<span class="kw">fn</span> <span class="ident">twice</span>(<span class="ident">wrapper</span>: <span class="ident">Either</span><span class="op"><</span><span class="ident">u32</span>, <span class="kw-2">&</span><span class="ident">str</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Either</span><span class="op"><</span><span class="ident">u32</span>, <span class="kw-2">&</span><span class="ident">str</span><span class="op">></span> {
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<span class="kw">let</span> <span class="ident">value</span> <span class="op">=</span> <span class="macro">try_left</span><span class="macro">!</span>(<span class="ident">wrapper</span>);
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<span class="ident">Left</span>(<span class="ident">value</span> <span class="op">*</span> <span class="number">2</span>)
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}
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<span class="kw">fn</span> <span class="ident">main</span>() {
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">twice</span>(<span class="ident">Left</span>(<span class="number">2</span>)), <span class="ident">Left</span>(<span class="number">4</span>));
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">twice</span>(<span class="ident">Right</span>(<span class="string">"ups"</span>)), <span class="ident">Right</span>(<span class="string">"ups"</span>));
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}</pre>
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