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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 `parser` fn in crate `combine`."><meta name="keywords" content="rust, rustlang, rust-lang, parser"><title>combine::combinator::parser - 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></head><body class="rustdoc fn"><!--[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">☰</div><div class="sidebar-elems"><p class='location'><a href='../index.html'>combine</a>::<wbr><a href='index.html'>combinator</a></p><script>window.sidebarCurrent = {name: 'parser', ty: 'fn', 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"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><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='in-band'>Function <a href='../index.html'>combine</a>::<wbr><a href='index.html'>combinator</a>::<wbr><a class="fn" href=''>parser</a></span><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'>−</span>]</a></span><a class='srclink' href='../../src/combine/combinator.rs.html#1481-1487' title='goto source code'>[src]</a></span></h1><pre class='rust fn'>pub fn parser<I, O, F>(f: F) -> <a class="struct" href="../../combine/combinator/struct.FnParser.html" title="struct combine::combinator::FnParser">FnParser</a><I, F> <span class="where fmt-newline">where<br> I: <a class="trait" href="../../combine/trait.Stream.html" title="trait combine::Stream">Stream</a>,<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnMut.html" title="trait core::ops::function::FnMut">FnMut</a>(I) -> <a class="type" href="../../combine/type.ParseResult.html" title="type combine::ParseResult">ParseResult</a><O, I>, </span></pre><div class='docblock'><p>Wraps a function, turning it into a parser.</p>
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<p>Mainly needed to turn closures into parsers as function types can be casted to function pointers
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to make them usable as a parser.</p>
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<pre class="rust rust-example-rendered">
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<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">combine</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">even_digit</span> <span class="op">=</span> <span class="ident">parser</span>(<span class="op">|</span><span class="ident">input</span><span class="op">|</span> {
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<span class="comment">// Help type inference out</span>
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<span class="kw">let</span> <span class="kw">_</span>: <span class="kw-2">&</span><span class="ident">str</span> <span class="op">=</span> <span class="ident">input</span>;
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<span class="kw">let</span> <span class="ident">position</span> <span class="op">=</span> <span class="ident">input</span>.<span class="ident">position</span>();
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<span class="kw">let</span> (<span class="ident">char_digit</span>, <span class="ident">input</span>) <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">digit</span>().<span class="ident">parse_stream</span>(<span class="ident">input</span>));
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<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> (<span class="ident">char_digit</span> <span class="kw">as</span> <span class="ident">i32</span>) <span class="op">-</span> (<span class="string">'0'</span> <span class="kw">as</span> <span class="ident">i32</span>);
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<span class="kw">if</span> <span class="ident">d</span> <span class="op">%</span> <span class="number">2</span> <span class="op">==</span> <span class="number">0</span> {
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<span class="prelude-val">Ok</span>((<span class="ident">d</span>, <span class="ident">input</span>))
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}
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<span class="kw">else</span> {
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<span class="comment">//Return an empty error since we only tested the first token of the stream</span>
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<span class="kw">let</span> <span class="ident">errors</span> <span class="op">=</span> <span class="ident">ParseError</span>::<span class="ident">new</span>(<span class="ident">position</span>, <span class="ident">Error</span>::<span class="ident">Expected</span>(<span class="ident">From</span>::<span class="ident">from</span>(<span class="string">"even number"</span>)));
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<span class="prelude-val">Err</span>(<span class="ident">Consumed</span>::<span class="ident">Empty</span>(<span class="ident">errors</span>))
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}
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});
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<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">even_digit</span>
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.<span class="ident">parse</span>(<span class="string">"8"</span>)
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.<span class="ident">map</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> <span class="ident">x</span>.<span class="number">0</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>, <span class="prelude-val">Ok</span>(<span class="number">8</span>));</pre>
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