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<h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>syn</a>::<wbr><a class="macro" href=''>map</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/syn/parsers.rs.html#189-202' title='goto source code'>[src]</a></span></h1>
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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">map</span> {
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(<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="macro-nonterminal">$</span><span class="macro-nonterminal">g</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">f</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">g</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
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}</pre>
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<div class='docblock'><p>Transform the result of a parser by applying a function or closure.</p>
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<ul>
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<li><strong>Syntax:</strong> <code>map!(THING, FN)</code></li>
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<li><strong>Output:</strong> the return type of function FN applied to THING</li>
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</ul>
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<pre class="rust rust-example-rendered">
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<span class="attribute">#[<span class="ident">macro_use</span>]</span>
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<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">syn</span>;
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<span class="kw">use</span> <span class="ident">syn</span>::{<span class="ident">Expr</span>, <span class="ident">ExprIf</span>};
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<span class="doccomment">/// Extracts the branch condition of an `if`-expression.</span>
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<span class="kw">fn</span> <span class="ident">get_cond</span>(<span class="ident">if_</span>: <span class="ident">ExprIf</span>) <span class="op">-></span> <span class="ident">Expr</span> {
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<span class="kw-2">*</span><span class="ident">if_</span>.<span class="ident">cond</span>
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}
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<span class="doccomment">/// Parses a full `if`-expression but returns the condition part only.</span>
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<span class="doccomment">///</span>
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<span class="doccomment">/// Example: `if x > 0xFF { "big" } else { "small" }`</span>
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<span class="doccomment">/// The return would be the expression `x > 0xFF`.</span>
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<span class="macro">named</span><span class="macro">!</span>(<span class="ident">if_condition</span> <span class="op">-></span> <span class="ident">Expr</span>,
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<span class="macro">map</span><span class="macro">!</span>(<span class="macro">syn</span><span class="macro">!</span>(<span class="ident">ExprIf</span>), <span class="ident">get_cond</span>)
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);
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<span class="doccomment">/// Equivalent using a closure.</span>
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<span class="macro">named</span><span class="macro">!</span>(<span class="ident">if_condition2</span> <span class="op">-></span> <span class="ident">Expr</span>,
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<span class="macro">map</span><span class="macro">!</span>(<span class="macro">syn</span><span class="macro">!</span>(<span class="ident">ExprIf</span>), <span class="op">|</span><span class="ident">if_</span><span class="op">|</span> <span class="kw-2">*</span><span class="ident">if_</span>.<span class="ident">cond</span>)
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);</pre>
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<p><em>This macro is available if Syn is built with the <code>"parsing"</code> feature.</em></p>
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