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<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>synom</a>::<wbr><a class="macro" href=''>option</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/synom/helper.rs.html#120-131' title='goto source code'>[src]</a></span></h1>
<pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">option</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=></span> { ... };
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">f</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
}</pre>
<div class='docblock'><p>Turn a failed parse into <code>None</code> and a successful parse into <code>Some</code>.</p>
<ul>
<li><strong>Syntax:</strong> <code>option!(THING)</code></li>
<li><strong>Output:</strong> <code>Option<THING></code></li>
</ul>
<pre class="rust rust-example-rendered">
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">syn</span>;
<span class="attribute">#[<span class="ident">macro_use</span>]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">synom</span>;
<span class="macro">named</span><span class="macro">!</span>(<span class="ident">maybe_bang</span> <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">str</span><span class="op">></span>, <span class="macro">option</span><span class="macro">!</span>(<span class="macro">punct</span><span class="macro">!</span>(<span class="string">"!"</span>)));
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="kw">let</span> <span class="ident">input</span> <span class="op">=</span> <span class="string">"!"</span>;
<span class="kw">let</span> <span class="ident">parsed</span> <span class="op">=</span> <span class="ident">maybe_bang</span>(<span class="ident">input</span>).<span class="ident">expect</span>(<span class="string">"maybe bang"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">parsed</span>, <span class="prelude-val">Some</span>(<span class="string">"!"</span>));
<span class="kw">let</span> <span class="ident">input</span> <span class="op">=</span> <span class="string">""</span>;
<span class="kw">let</span> <span class="ident">parsed</span> <span class="op">=</span> <span class="ident">maybe_bang</span>(<span class="ident">input</span>).<span class="ident">expect</span>(<span class="string">"maybe bang"</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">parsed</span>, <span class="prelude-val">None</span>);
}</pre>
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