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nom 0.3.9

A byte oriented, zero copy, parser combinators library
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<h1 class='fqn'><span class='in-band'><a href='index.html'>nom</a>::<wbr><a class='macro' href=''>chain!</a></span><span class='out-of-band'><span id='render-detail'>
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                [<span class='inner'>&#x2212;</span>]
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        </span><a id='src-7390' class='srclink' href='../src/nom/macros.rs.html#414-418' 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'>chain</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'>rest</span>:<span class='ident'>tt</span>)<span class='op'>*</span>) <span class='op'>=&gt;</span> (
    <span class='macro'>chaining_parser</span><span class='macro'>!</span>(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>i</span>, $(<span class='macro-nonterminal'>$</span><span class='macro-nonterminal'>rest</span>)<span class='op'>*</span>)
  );
);
</pre>
<div class='docblock'><p>chains parsers and assemble the results through a closure</p>
<pre class='rust rust-example-rendered'>
<span class='attribute'>#[<span class='ident'>derive</span>(<span class='ident'>PartialEq</span>,<span class='ident'>Eq</span>,<span class='ident'>Debug</span>)]</span>
<span class='kw'>struct</span> <span class='ident'>B</span> {
  <span class='ident'>a</span>: <span class='ident'>u8</span>,
  <span class='ident'>b</span>: <span class='prelude-ty'>Option</span><span class='op'>&lt;</span><span class='ident'>u8</span><span class='op'>&gt;</span>
}

<span class='macro'>named</span><span class='macro'>!</span>(<span class='ident'>y</span>, <span class='macro'>tag</span><span class='macro'>!</span>(<span class='string'>&quot;efgh&quot;</span>));

<span class='kw'>fn</span> <span class='ident'>ret_int</span>(<span class='ident'>i</span>:<span class='kw-2'>&amp;</span>[<span class='ident'>u8</span>]) <span class='op'>-&gt;</span> <span class='ident'>IResult</span><span class='op'>&lt;</span><span class='kw-2'>&amp;</span>[<span class='ident'>u8</span>], <span class='ident'>u8</span><span class='op'>&gt;</span> { <span class='ident'>Done</span>(<span class='ident'>i</span>, <span class='number'>1</span>) }
<span class='macro'>named</span><span class='macro'>!</span>(<span class='ident'>ret_y</span><span class='op'>&lt;</span><span class='kw-2'>&amp;</span>[<span class='ident'>u8</span>], <span class='ident'>u8</span><span class='op'>&gt;</span>, <span class='macro'>map</span><span class='macro'>!</span>(<span class='ident'>y</span>, <span class='op'>|</span>_<span class='op'>|</span> <span class='number'>1</span>)); <span class='comment'>// return 1 if the &quot;efgh&quot; tag is found</span>

 <span class='macro'>named</span><span class='macro'>!</span>(<span class='ident'>z</span><span class='op'>&lt;</span><span class='kw-2'>&amp;</span>[<span class='ident'>u8</span>], <span class='ident'>B</span><span class='op'>&gt;</span>,
   <span class='macro'>chain</span><span class='macro'>!</span>(
     <span class='macro'>tag</span><span class='macro'>!</span>(<span class='string'>&quot;abcd&quot;</span>)  <span class='kw-2'>~</span>
     <span class='ident'>aa</span>: <span class='ident'>ret_int</span>   <span class='kw-2'>~</span>     <span class='comment'>// the result of that parser will be used in the closure</span>
     <span class='macro'>tag</span><span class='macro'>!</span>(<span class='string'>&quot;abcd&quot;</span>)? <span class='kw-2'>~</span>     <span class='comment'>// this parser is optional</span>
     <span class='ident'>bb</span>: <span class='ident'>ret_y</span>?    ,     <span class='comment'>// the result of that parser is an option</span>
     <span class='op'>||</span>{<span class='ident'>B</span>{<span class='ident'>a</span>: <span class='ident'>aa</span>, <span class='ident'>b</span>: <span class='ident'>bb</span>}}
   )
 );

<span class='comment'>// the first &quot;abcd&quot; tag is not present, we have an error</span>
<span class='kw'>let</span> <span class='ident'>r1</span> <span class='op'>=</span> <span class='ident'>z</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;efgh&quot;</span>[..]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>r1</span>, <span class='ident'>Error</span>(<span class='ident'>Position</span>(<span class='number'>0</span>,<span class='kw-2'>&amp;</span><span class='string'>b&quot;efgh&quot;</span>[..])));

<span class='comment'>// everything is present, everything is parsed</span>
<span class='kw'>let</span> <span class='ident'>r2</span> <span class='op'>=</span> <span class='ident'>z</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;abcdabcdefgh&quot;</span>[..]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>r2</span>, <span class='ident'>Done</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;&quot;</span>[..], <span class='ident'>B</span>{<span class='ident'>a</span>: <span class='number'>1</span>, <span class='ident'>b</span>: <span class='prelude-val'>Some</span>(<span class='number'>1</span>)}));

<span class='comment'>// the second &quot;abcd&quot; tag is optional</span>
<span class='kw'>let</span> <span class='ident'>r3</span> <span class='op'>=</span> <span class='ident'>z</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;abcdefgh&quot;</span>[..]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>r3</span>, <span class='ident'>Done</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;&quot;</span>[..], <span class='ident'>B</span>{<span class='ident'>a</span>: <span class='number'>1</span>, <span class='ident'>b</span>: <span class='prelude-val'>Some</span>(<span class='number'>1</span>)}));

<span class='comment'>// the result of ret_y is optional, as seen in the B structure</span>
<span class='kw'>let</span> <span class='ident'>r4</span> <span class='op'>=</span> <span class='ident'>z</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;abcdabcdwxyz&quot;</span>[..]);
<span class='macro'>assert_eq</span><span class='macro'>!</span>(<span class='ident'>r4</span>, <span class='ident'>Done</span>(<span class='kw-2'>&amp;</span><span class='string'>b&quot;wxyz&quot;</span>[..], <span class='ident'>B</span>{<span class='ident'>a</span>: <span class='number'>1</span>, <span class='ident'>b</span>: <span class='prelude-val'>None</span>}));
</pre>
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