Boost Spirit X3 eol unexpected behaviour - c++

Question

This question in strictly related to boost-spirit-x3-parse-into-structs
I have this grammar
#include <iostream>
//#define BOOST_SPIRIT_X3_DEBUG
#include <boost/spirit/home/x3.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
struct sectionInfo
{
std::string name;
int number = 0;
float pitch = 0.0f;
int visible = 0;
float minCutsTblSize = 0.0f;
//technology section attributes
float gridResolution = 0.0f;
float lengthPrecision = 0.0f;
};
const char START_SECTION = '{';
const char END_SECTION = '}';
const char QUOTE = '"';
const char EQUALS = '=';
const char* LAYER_SECTION = "Layer";
const char* TECHNOLOGY_SECTION = "Technology";
const char* NUMBER_ATTR = "layerNumber";
const char* VISIBLE_ATTR = "visible";
const char* COLOR_ATTR = "color";
const char* PITCH_ATTR = "pitch";
const char* MIN_CUTS_TBL_SIZE_ATTR = "minCutsTblSize";
const char* GRID_RESOLUTION_ATTR = "gridResolution";
const char* LENGTH_PRECISION_ATTR = "lengthPrecision";
namespace Parser {
namespace x3 = boost::spirit::x3;
namespace detail {
template <typename T> auto propagate(T member) {
return [=](auto& ctx) { x3::traits::move_to(x3::_attr(ctx), x3::_val(ctx).*member); };
}
template <typename T = sectionInfo, typename P>
auto rule(const char* debug, P p) { return x3::rule<struct _, T> {debug} = x3::skip(x3::space)[p]; };
auto quoted = rule<std::string>("quoted", x3::lexeme[QUOTE >> +(x3::char_ - QUOTE) >> QUOTE]);
template <typename T> auto make_member_parser(bool T::* const member) { return x3::bool_[propagate(member)]; }
template <typename T> auto make_member_parser(int T::* const member) { return x3::int_[propagate(member)]; }
template <typename T> auto make_member_parser(double T::* const member) { return x3::double_[propagate(member)]; }
template <typename T> auto make_member_parser(float T::* const member) { return x3::double_[propagate(member)]; }
template <typename T> auto make_member_parser(std::string T::* const member) { return quoted[propagate(member)]; }
auto property = [](auto label, auto member) {
return x3::as_parser(label) >> EQUALS >> make_member_parser(member);
};
}
using detail::rule;
using detail::propagate;
using detail::property;
using detail::quoted;
auto number = property(NUMBER_ATTR, &sectionInfo::number);
auto visible = property(VISIBLE_ATTR, &sectionInfo::visible);
auto pitch = property(PITCH_ATTR, &sectionInfo::pitch);
auto minCutsTblSize = property(MIN_CUTS_TBL_SIZE_ATTR, &sectionInfo::minCutsTblSize);
auto lengthPrecision = property(LENGTH_PRECISION_ATTR, &sectionInfo::lengthPrecision);
auto gridResolution = property(GRID_RESOLUTION_ATTR, &sectionInfo::gridResolution);
auto skipLine = *(x3::char_ - x3::eol);
x3::rule<struct sectionInfoId, sectionInfo> const layer = "layer";
x3::rule<struct mainRuleId, std::vector<sectionInfo>> const mainRule = "mainRule";
auto layer_def =
LAYER_SECTION >> quoted[propagate(&sectionInfo::name)] >> START_SECTION >> x3::eol
>> *( (number | visible | pitch | minCutsTblSize | lengthPrecision | gridResolution) >> +x3::eol )
>> END_SECTION;
auto skipper = x3::blank;
auto mainRule_def = *(*x3::eol >> layer >> *x3::eol);
BOOST_SPIRIT_DEFINE(layer, mainRule);
}
std::ostream& operator<<(std::ostream& os, const sectionInfo& s)
{
os
<< "name=" << " " << s.name << "\n"
<< "number=" << " " << s.number << "\n"
<< "visible=" << " " << s.visible << "\n"
<< "pitch=" << " " << s.pitch << "\n"
<< "minCutsTblSize=" << " " << s.minCutsTblSize << "\n"
<< "lengthPrecision=" << " " << s.lengthPrecision << "\n"
<< "gridResolution=" << " " << s.gridResolution << "\n\n";
return os;
}
int main() {
std::stringstream ss;
ss
<<"\r\nLayer \"UBMB\" {\r\n"
<< " layerNumber = 170\r\n"
<< " pitch = 33.6\r\n"
<< "}\r\n"
<< "\r\n"
<< "Layer \"RV\" {\r\n"
<< " gridResolution = 0.34\r\n"
<< " minCutsTblSize = 22.7\r\n"
<< " layerNumber = 85\r\n"
<< " visible = 2\r\n"
<< " pitch = 331\r\n"
<< "}\r\n"
<< " \r\n"
<< "Layer \"foffo\" {\r\n"
<< " layerNumber = 125\r\n"
<< " pitch = 0.005\r\n"
<< " gridResolution = 21.7\r\n"
<< " lengthPrecision = 0.15\r\n"
<< "}\r\n"
<< "\r\n";
std::vector<sectionInfo> sections;
auto sample = ss.str();
auto f = sample.begin(), l = sample.end();
bool ok = boost::spirit::x3::phrase_parse(
f, l,
Parser::mainRule,
Parser::skipper,
sections
);
if (ok && f==l)
{
std::cout << "\n\n Parsed successfully \n\n";
for(auto& s : sections)
{
std::cout << s;
}
}
else
std::cout << "Parse failed\n";
}
which successfully parses the input:
output is:
name= UBMB
number= 170
visible= 0
pitch= 33.6
minCutsTblSize= 0
lengthPrecision= 0
gridResolution= 0
name= RV
number= 85
visible= 2
pitch= 331
minCutsTblSize= 22.7
lengthPrecision= 0
gridResolution= 0.34
name= foffo
number= 125
visible= 0
pitch= 0.005
minCutsTblSize= 0
lengthPrecision= 0.15
gridResolution= 21.7
The problem arises because I need to skip some lines, i.e. the lines with properties not of interest (not defined in my grammar)
edit: For example, there may be a property dummy = "foo" which I want to skip.
To achieve this, the layer rule
auto layer_def = LAYER_SECTION >> quoted[propagate(&sectionInfo::name)] >> START_SECTION >> x3::eol
>> *( (number | visible | pitch | minCutsTblSize | lengthPrecision | gridResolution ) >> +x3::eol )
>> END_SECTION;
becomes
auto layer_def = LAYER_SECTION >> quoted[propagate(&sectionInfo::name)] >> START_SECTION >> x3::eol
>> *( (number | visible | pitch | minCutsTblSize | lengthPrecision | gridResolution | skipLine) >> +x3::eol )
>> END_SECTION;
The parser succeeds, but the output is now
name= UBMB number= 125 visible= 2 pitch= 0.005 minCutsTblSize= 22.7
lengthPrecision= 0.15 gridResolution= 21.7
which is wrong (only one section, properties taken here and there...)
It is evident the problem resides in the skipLine rule
auto skipLine = *(x3::char_ - x3::eol);
and I can't figure out why.
I thought it was obvious that the rule *(char - eol) >> eol
would match any line, but I guess it isn't..
Any clues?

Answer 1

Firstly, I'd simplify skipping. The skipper doesn't belong in the call-site because it's important to the grammar. Encapsulate it into the mainRule, and simplify:
auto mainRule_def = x3::skip(x3::blank) [ -layer % x3::eol ];
The -layer expression is a trick that accepts empty lines. Now using the parser becomes:
bool ok = boost::spirit::x3::parse(f, l, Parser::mainRule, sections);
Next: skipLine eats '}' as well, making everything fall apart: everything after that is taken as (invalid) properties for the same layer, and finally there is no END_SECTION so the grammar fails to match.
Simply:
auto skipLine = *(x3::char_ - x3::eol - END_SECTION);
Pro Tip:
When in doubt, debug: Live On Coliru
// debug it
auto skipLine = x3::rule<struct skipLine_> {"skipLine"} = *(x3::char_ - x3::eol/* - END_SECTION*/);
Full Demo
With some minor simplifications
Live On Coliru
#include <iostream>
#define BOOST_SPIRIT_X3_DEBUG
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/io.hpp>
#include <boost/spirit/home/x3.hpp>
struct sectionInfo {
std::string name;
int number = 0;
float pitch = 0.0f;
int visible = 0;
float minCutsTblSize = 0.0f;
// technology section attributes
float gridResolution = 0.0f;
float lengthPrecision = 0.0f;
};
char const START_SECTION = '{';
char const END_SECTION = '}';
char const QUOTE = '"';
char const EQUALS = '=';
char const* LAYER_SECTION = "Layer";
char const* TECHNOLOGY_SECTION = "Technology";
char const* NUMBER_ATTR = "layerNumber";
char const* VISIBLE_ATTR = "visible";
char const* COLOR_ATTR = "color";
char const* PITCH_ATTR = "pitch";
char const* MIN_CUTS_TBL_SIZE_ATTR = "minCutsTblSize";
char const* GRID_RESOLUTION_ATTR = "gridResolution";
char const* LENGTH_PRECISION_ATTR = "lengthPrecision";
namespace Parser {
namespace x3 = boost::spirit::x3;
namespace detail {
template <typename T> auto propagate(T member) {
return [=](auto &ctx) { x3::traits::move_to(x3::_attr(ctx), x3::_val(ctx).*member); };
}
template <typename T = sectionInfo, typename P> auto rule(const char *debug, P p) {
return x3::rule<struct _, T>{ debug } = x3::skip(x3::space)[p];
};
auto quoted = rule<std::string>("quoted", x3::lexeme[QUOTE >> +(x3::char_ - QUOTE) >> QUOTE]);
#define MMP_(T, p) template <typename U> auto make_member_parser(T U::*const member) { return (p)[propagate(member)]; }
MMP_(bool, x3::bool_);
MMP_(int, x3::int_);
MMP_(double, x3::double_);
MMP_(float, x3::double_);
MMP_(std::string, quoted);
#undef MMP_
auto property = [](auto label, auto member) { return x3::as_parser(label) >> EQUALS >> make_member_parser(member); };
}
using detail::rule;
using detail::propagate;
using detail::property;
using detail::quoted;
auto number = property(NUMBER_ATTR, &sectionInfo::number);
auto visible = property(VISIBLE_ATTR, &sectionInfo::visible);
auto pitch = property(PITCH_ATTR, &sectionInfo::pitch);
auto minCutsTblSize = property(MIN_CUTS_TBL_SIZE_ATTR, &sectionInfo::minCutsTblSize);
auto lengthPrecision = property(LENGTH_PRECISION_ATTR, &sectionInfo::lengthPrecision);
auto gridResolution = property(GRID_RESOLUTION_ATTR, &sectionInfo::gridResolution);
auto skipLine = *(x3::char_ - x3::eol - END_SECTION);
x3::rule<struct sectionInfoId, sectionInfo> const layer = "layer";
x3::rule<struct mainRuleId, std::vector<sectionInfo> > const mainRule = "mainRule";
auto layer_def =
LAYER_SECTION >> quoted[propagate(&sectionInfo::name)]
>> START_SECTION >> x3::eol
>> *((number | visible | pitch | minCutsTblSize | lengthPrecision | gridResolution | skipLine) >> +x3::eol)
>> END_SECTION
;
auto mainRule_def = x3::skip(x3::blank) [ -layer % x3::eol ];
BOOST_SPIRIT_DEFINE(layer, mainRule);
}
std::ostream &operator<<(std::ostream &os, const sectionInfo &s) {
return os
<< "name=" << " " << s.name << "\n"
<< "number=" << " " << s.number << "\n"
<< "visible=" << " " << s.visible << "\n"
<< "pitch=" << " " << s.pitch << "\n"
<< "minCutsTblSize=" << " " << s.minCutsTblSize << "\n"
<< "lengthPrecision=" << " " << s.lengthPrecision << "\n"
<< "gridResolution=" << " " << s.gridResolution << "\n\n";
}
int main() {
std::string const sample =
"\r\nLayer \"UBMB\" {\r\n"
" layerNumber = 170\r\n"
" pitch = 33.6\r\n"
"}\r\n"
"\r\n"
"Layer \"RV\" {\r\n"
" gridResolution = 0.34\r\n"
" minCutsTblSize = 22.7\r\n"
" layerNumber = 85\r\n"
" visible = 2\r\n"
" pitch = 331\r\n"
"}\r\n"
" \r\n"
"Layer \"foffo\" {\r\n"
" layerNumber = 125\r\n"
" pitch = 0.005\r\n"
" gridResolution = 21.7\r\n"
" lengthPrecision = 0.15\r\n"
"}\r\n"
"\r\n";
std::vector<sectionInfo> sections;
{
auto f = sample.begin(), l = sample.end();
bool ok = boost::spirit::x3::parse(f, l, Parser::mainRule, sections);
if (ok && f == l) {
std::cout << "\n\n Parsed successfully \n\n";
for (auto &s : sections) {
std::cout << s;
}
} else
std::cout << "Parse failed\n";
}
}
Prints
Parsed successfully
name= UBMB
number= 170
visible= 0
pitch= 33.6
minCutsTblSize= 0
lengthPrecision= 0
gridResolution= 0
name= RV
number= 85
visible= 2
pitch= 331
minCutsTblSize= 22.7
lengthPrecision= 0
gridResolution= 0.34
name= foffo
number= 125
visible= 0
pitch= 0.005
minCutsTblSize= 0
lengthPrecision= 0.15
gridResolution= 21.7