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POSetting attributes from semantic action(s) for expression passed into qi::phrase_parse
 

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  1. POSetting attributes from semantic action(s) for expression passed into qi::phrase_parse
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    <p>During parsing I have a few attributes that I need to set in semantic action only ( as they are derived from data being parsed and I want to avoid <code>global</code> variables and dependency on <code>BOOST_FUSION_ADAPT_STRUCT</code> as well as my code should be generic so that I can reuse it for multiple types). If I use more than one variable passed into <code>qi::phrase_parse</code> I get very long list of compilation errors. I need a help badly :-)</p> <pre><code>#define BOOST_RESULT_OF_USE_DECLTYPE #define BOOST_SPIRIT_USE_PHOENIX_V3 #include &lt;boost/function.hpp&gt; #include &lt;boost/phoenix/fusion.hpp&gt; #include &lt;boost/spirit/include/phoenix.hpp&gt; #include &lt;boost/spirit/include/qi.hpp&gt; #include &lt;iostream&gt; #include &lt;string&gt; #include &lt;climits&gt; namespace qi = boost::spirit::qi; namespace ph = boost::phoenix; namespace ascii = boost::spirit::ascii; int main( int argc, char**argv ) { bool rc; std::string input(""); //Test case 1 works fine { auto iter( input.begin() ); auto last( input.end() ); int val1=33; rc = qi::phrase_parse( iter, last, qi::eps[ qi::_val=11 ] , ascii::space, val1 ) &amp;&amp; iter==last; if( rc ) std::cout &lt;&lt; "val1=" &lt;&lt; val1 &lt;&lt; std::endl; } //Test case 2 does not compile { auto iter( input.begin() ); auto last( input.end() ); int val1=33; int val2=0; rc = qi::phrase_parse( iter, last, qi::eps[ ph::at_c&lt;0&gt;(qi::_val)=1,ph::at_c&lt;1&gt;(qi::_val)=2 ], ascii::space, val1,val2 ) &amp;&amp; iter==last; if( rc ) std::cout &lt;&lt; "val1=" &lt;&lt; val1 &lt;&lt; " val2=" &lt;&lt; val2 &lt;&lt; std::endl; } //Test case 3 works fine { auto iter( input.begin() ); auto last( input.end() ); int val1=33; int val2=0; rc = qi::phrase_parse( iter, last, qi::attr(1)&gt;&gt;qi::attr(2), ascii::space, val1,val2 ) &amp;&amp; iter==last; if( rc ) std::cout &lt;&lt; "val1=" &lt;&lt; val1 &lt;&lt; " val2=" &lt;&lt; val2 &lt;&lt; std::endl; } return 0; } </code></pre> <p>I took the "customized" my_phrase_parse from <code>cv_and_he</code> but it breaks compilation on the full test case that I want to get running:</p> <pre><code>template&lt;typename T,typename R&gt; void testParser( R rule ) { for ( const auto input : std::vector&lt; std::string &gt;{ "5 1.0 2.0 3.0 4.0 5.0", "1 1.0", "0" , "", "2 3 ab" } ) { bool rc; T maxValue; T minValue; auto iter( input.begin() ); auto last( input.end() ); std::vector&lt; T &gt; v; rc = my_phrase_parse( iter, last, qi::eps[ ph::at_c&lt;0&gt;(qi::_val)=std::numeric_limits&lt;T&gt;::max(), ph::at_c&lt;1&gt;(qi::_val)=std::numeric_limits&lt;T&gt;::min() ] &gt;&gt; -( qi::omit[ qi::int_] &gt;&gt; *rule[ ph::if_(ph::at_c&lt;0&gt;(qi::_val)&gt;qi::_1)[ ph::at_c&lt;0&gt;(qi::_val)=qi::_1 ], ph::if_(ph::at_c&lt;1&gt;(qi::_val)&lt;qi::_1)[ ph::at_c&lt;1&gt;(qi::_val)=qi::_1 ] ] ) ,ascii::space, minValue, maxValue,v ) &amp;&amp; iter==last; std::cout &lt;&lt; ( rc ? "ok :`" : "err:`" ) &lt;&lt; input &lt;&lt; "` -&gt; "; if( rc ) { std::cout &lt;&lt; "min=" &lt;&lt; minValue &lt;&lt; " max=" &lt;&lt; maxValue &lt;&lt; "\t"; std::copy( v.begin(), v.end(), std::ostream_iterator&lt;T&gt;( std::cout," " )); } else std::cout &lt;&lt; *iter; std::cout &lt;&lt; std::endl; } } ... testParser&lt;double&gt;( qi::double_ ); </code></pre>
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    1. CO[Before Boost 1.47.0 your first example wouldn't work](http://boost-spirit.com/home/2011/02/26/using-_val-in-top-level-semantic-actions/). In that version a fix was applied to the "normal" `parse` and `phrase_parse`, but apparently not to the "variadic" ones. If you create a rule like `qi::rule<decltype(iter),fusion::vector<int&, int&>(),ascii::space_type> parser=qi::eps[ ph::at_c<0>(qi::_val)=1,ph::at_c<1>(qi::_val)=2 ];` it will work.
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    2. CO@cv_and_he Hi, Thanks for your feedback. I'm using 1_52. if the single variable case did not work I would not have asked the question as it would have been obvious :-) because I can avoid the problem with `test case 3` generating the values using attr.
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    3. COI know it works. If you read the link, you see that the only reason that it works is because it was changed for `parse` and `phrase_parse` with a single attribute only.
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