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POBoost Spirit - Parser Capturing Unwanted Text
 

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    <p>I have a simple struct </p> <pre><code>// in namespace client struct UnaryExpression { std::string key; SomeEnums::CompareType op; }; </code></pre> <p><code>SomeEnums::CompareType</code> is an enum where I define a symbol table as such:</p> <pre><code>struct UnaryOps : bsq::symbols&lt;char, SomeEnums::CompareType&gt; { UnaryOps() : bsq::symbols&lt;char, SomeEnums::CompareType&gt;(std::string("UnaryOps")) { add("exists", SomeEnums::Exists) ("nexists", SomeEnums::NotExists); } }; </code></pre> <p>I have two different ways I want to parse the struct, which I asked about in <a href="https://stackoverflow.com/questions/14514983/boost-spitirt-single-struct-multiple-rules">another thread</a> and got to work (mostly).</p> <p>My grammar looks as follows:</p> <pre><code>template&lt;typename Iterator&gt; struct test_parser : bsq::grammar&lt;Iterator, client::UnaryExpression(), bsq::ascii::space_type&gt; { test_parser() : test_parser::base_type(unaryExp, std::string("Test")) { using bsq::no_case; key %= bsq::lexeme[bsq::alnum &gt;&gt; +(bsq::alnum | bsq::char_('.'))]; unaryExp %= unaryE | unaryF; unaryE %= key &gt;&gt; no_case[unaryOps]; unaryF %= no_case[unaryOps] &gt;&gt; '(' &gt;&gt; key &gt;&gt; ')'; }; UnaryOps unaryOps; bsq::rule&lt;Iterator, std::string(), bsq::ascii::space_type&gt; key; bsq::rule&lt;Iterator, client::UnaryExpression(), bsq::ascii::space_type&gt; unaryExp; bsq::rule&lt;Iterator, client::UnaryExpression(), bsq::ascii::space_type&gt; unaryE; bsq::rule&lt;Iterator, client::UnaryFunction(), bsq::ascii::space_type&gt; unaryF; }; </code></pre> <p>And I'm parsing the code using the following logic:</p> <pre><code>bool r = phrase_parse(iter, end, parser, bsq::ascii::space, exp); if (r &amp;&amp; iter == end) { std::cout &lt;&lt; "-------------------------\n"; std::cout &lt;&lt; "Parsing succeeded\n"; std::cout &lt;&lt; "key: " &lt;&lt; exp.key &lt;&lt; "\n"; std::cout &lt;&lt; "op : " &lt;&lt; exp.op &lt;&lt; "\n"; std::cout &lt;&lt; "-------------------------\n"; } </code></pre> <p>This all works fine if I do the input like <code>foo exists</code> and exp.key equals "foo" and exp.op equals the corresponding enum value (in this case 0). Something like <code>foo1 nexists</code> also works.</p> <p>However, that second rule doesn't work like I expect. If I give it input of <code>nexists(foo)</code> then I get the following output:</p> <pre><code>------------------------- Parsing succeeded key: nexistsfoo op : 1 ------------------------- </code></pre> <p>It seems that the enum value is getting set appropriately but I can't figure out why the "nexsts" is getting prepended to the key string. Can someone please tell me how I can fix my rule so that the key would equal just 'foo' with the second rule? </p> <p>I have posted a copy of the stripped down code that illustrates my problem here: <a href="http://pastebin.com/402M9iTS" rel="nofollow noreferrer">http://pastebin.com/402M9iTS</a> </p>
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    1. COI'm not sure why but changing `unaryExp %= unaryE | unaryF;` to `unaryExp %= unaryF | unaryE;` solved the problem
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    2. COYou can find an explanation to the same problem here. Your solution is better (and with a cleaner grammar) since it doesn't need to keep temporary copies but another alternative is using [qi::hold](http://www.boost.org/libs/spirit/doc/html/spirit/qi/reference/directive/hold.h‌​tml). Your rule would then be: `unaryExp %= bsq::hold[unaryE] | unaryF;`.
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    3. CO@llonesmiz Did you intend to post a link with that?
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