| <!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="Creates a parser from a function which takes a function that are given the actual parser. Though convoluted this makes it possible to hide the concrete parser type without `Box` or losing the full information about the parser as is the case of `parser`."><meta name="keywords" content="rust, rustlang, rust-lang, opaque"><title>opaque in combine::parser::combinator - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../../combine/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../../combine/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In combine::parser::combinator</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Function <a href="../../index.html">combine</a>::<wbr><a href="../index.html">parser</a>::<wbr><a href="index.html">combinator</a>::<wbr><a class="fn" href="#">opaque</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../../../src/combine/parser/combinator.rs.html#1401-1408">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><pre class="rust fn"><code>pub fn opaque<Input, F, O, S>(f: F) -> <a class="struct" href="struct.Opaque.html" title="struct combine::parser::combinator::Opaque">Opaque</a><F, Input, O, S><span class="where fmt-newline">where<br> Input: <a class="trait" href="../../trait.Stream.html" title="trait combine::Stream">Stream</a>,<br> S: Default,<br> F: FnMut(&mut dyn FnMut(&mut dyn <a class="trait" href="../../trait.Parser.html" title="trait combine::Parser">Parser</a><Input, Output = O, PartialState = S>)),</span></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Creates a parser from a function which takes a function that are given the actual parser. |
| Though convoluted this makes it possible to hide the concrete parser type without <code>Box</code> or |
| losing the full information about the parser as is the case of <a href="../function/fn.parser.html"><code>parser</code></a>.</p> |
| <p>Since this hides the type this can also be useful for writing mutually recursive <code>impl Parser</code> |
| parsers to break the otherwise arbitrarily large type that rustc creates internally.</p> |
| <p>If you need a more general version (that does not need trait objects) try the <a href="../../macro.parser.html"><code>parser!</code></a> |
| macro.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code> |
| |
| <span class="attribute">#[derive(PartialEq, Debug)] |
| </span><span class="kw">enum </span>Expr { |
| Number(i64), |
| Pair(Box<Expr>, Box<Expr>), |
| } |
| |
| <span class="kw">fn </span>expr<Input>() -> FnOpaque<Input, Expr> |
| <span class="kw">where |
| </span>Input: Stream<Token = char>, |
| Input::Error: ParseError<Input::Token, Input::Range, Input::Position>, |
| { |
| <span class="macro">opaque!</span>( |
| <span class="comment">// `no_partial` disables partial parsing and replaces the partial state with `()`, |
| // letting us avoid naming that type |
| </span>no_partial(choice(( |
| from_str(many1::<String, <span class="kw">_</span>, <span class="kw">_</span>>(digit())) |
| .map(Expr::Number), |
| (char(<span class="string">'('</span>), expr(), char(<span class="string">','</span>), expr(), char(<span class="string">')'</span>)) |
| .map(|(<span class="kw">_</span>, l, <span class="kw">_</span>, r, <span class="kw">_</span>)| Expr::Pair(Box::new(l), Box::new(r))) |
| ))), |
| ) |
| } |
| |
| <span class="macro">assert_eq!</span>( |
| expr().easy_parse(<span class="string">"123"</span>), |
| <span class="prelude-val">Ok</span>((Expr::Number(<span class="number">123</span>), <span class="string">""</span>)) |
| ); |
| </code></pre></div> |
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