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POPassing file-path string to semantic action in Boost.Spirit
 

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  1. POPassing file-path string to semantic action in Boost.Spirit
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    <p>I am new to Boost.Spirit, and I have a question related to a mini-interpreter I am trying to implement using the library. As a sub-task of parsing my language, I need to extract a file-path from an input of the form:</p> <pre><code>"path = \"/path/to/file\"" </code></pre> <p>and pass it as a string (without quotes) to a semantic action.</p> <p>I wrote some code which can parse this type of input, but passing the parsed string does not work as expected, probably due to my lack of experience with Boost.Spirit.</p> <p>Can anyone help?</p> <p>In reality, my grammar is more complex, but I have isolated the problem to:</p> <pre><code>#include &lt;string&gt; #include "boost/spirit/include/qi.hpp" #include "boost/spirit/include/phoenix_core.hpp" #include "boost/spirit/include/phoenix_operator.hpp" namespace qi = boost::spirit::qi; namespace ascii = boost::spirit::ascii; namespace phoenix = boost::phoenix; namespace parser { // Semantic action (note: in reality, this would use file_path_string in non-trivial way) void display_path(std::string file_path_string) { std::cout &lt;&lt; "Detected file-path: " &lt;&lt; file_path_string &lt;&lt; std::endl; } // Grammar template &lt;typename Iterator&gt; struct path_command : qi::grammar&lt;Iterator, ascii::space_type&gt; { path_command() : path_command::base_type(path_specifier) { using qi::string; using qi::lit; path = +(qi::char_("/") &gt;&gt; *qi::char_("a-zA-Z_0-9")); quoted_path_string = lit('"') &gt;&gt; (path- lit('"')) &gt;&gt; lit('"'); path_specifier = lit("path") &gt;&gt; qi::lit("=") &gt;&gt; quoted_path_string[&amp;display_path]; } qi::rule&lt;Iterator, ascii::space_type&gt; path_specifier; qi::rule&lt;Iterator, std::string()&gt; path, quoted_path_string; }; } int main() { using ascii::space; typedef std::string::const_iterator iterator_type; typedef parser::path_command&lt;iterator_type&gt; path_command; bool parse_res; path_command command_instance; // Instance of our Grammar iterator_type iter, end; std::string test_command1 = "path = \"/file1\""; std::string test_command2 = "path = \"/dirname1/dirname2/file2\""; // Testing example command 1 iter = test_command1.begin(); end = test_command1.end(); parse_res = phrase_parse(iter, end, command_instance, space); std::cout &lt;&lt; "Parse result for test 1: " &lt;&lt; parse_res &lt;&lt; std::endl; // Testing example command 2 iter = test_command2.begin(); end = test_command2.end(); parse_res = phrase_parse(iter, end, command_instance, space); std::cout &lt;&lt; "Parse result for test 2: " &lt;&lt; parse_res &lt;&lt; std::endl; return EXIT_SUCCESS; } </code></pre> <p>The output is:</p> <pre><code>Detected file-path: / Parse result for test 1: 1 Detected file-path: /// Parse result for test 2: 1 </code></pre> <p>but I would like to obtain:</p> <pre><code>Detected file-path: /file1 Parse result for test 1: 1 Detected file-path: /dirname1/dirname2/file2 Parse result for test 2: 1 </code></pre>
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