Parsing escaped strings with boost spirit
I´m working with Spirit 2.4 and I'd want to parse a structure like this:
Text{text_field};
The point is that in text_field is a escaped string with the symbols '{', '}' and '\'. I would like to create a parser for this using qi. I've been trying this:
using boost::spirit::standard::char_;
using boost::spirit::standard::string;
using qi::lexeme;
using qi::lit;
qi::rule< IteratorT, std::string(), ascii::s开发者_Go百科pace_type > text;
qi::rule< IteratorT, std::string(), ascii::space_type > content;
qi::rule< IteratorT, std::string(), ascii::space_type > escChar;
text %=
lit( "Text" ) >> '{' >>
content >>
"};"
;
content %= lexeme[ +( +(char_ - ( lit( '\\' ) | '}' ) ) >> escChar ) ];
escChar %= string( "\\\\" )
| string( "\\{" )
| string( "\\}" );
But doesn't even compile. Any idea?
Your grammar could be written as:
qi::rule< IteratorT, std::string(), ascii::space_type > text;
qi::rule< IteratorT, std::string() > content;
qi::rule< IteratorT, char() > escChar;
text = "Text{" >> content >> "};";
content = +(~char_('}') | escChar);
escChar = '\\' >> char_("\\{}");
i.e.
text is
Text{
followed by content followed by}
content is at least one instance of either a character (but no
}
) or an escCharescChar is a single escaped
\\
,{
, or}
Note, the escChar rule now returns a single character and discards the escaping \\
. I'm not sure if that's what you need. Additionally, I removed the skipper for the content and escChar rules, which allows to leave off the lexeme[]
(a rule without skipper acts like an implicit lexeme).
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