Skipper does not work in boost::spirit - c++

Question

I use boost spirit to parse a color. That worked quite well,
but after I changed the the iterator type, the skipper stopped working.
"rgb(1.0,1.0,0.5)" // this works
" rgb(0.2,0.2,0.2)" // this fails
Here is the header:
struct ColorGrammar : public qi::grammar<StringIterator, Color(), chs::space_type>
{
//! Iterator type for this grammar
typedef StringIterator ItType;
//! Skipper type used in this grammar
typedef chs::space_type Skipper;
//! Rule to parse a number with up to 3 digits
qi::uint_parser<uint8, 10, 1, 3> number;
//! Rule to parse a hex digit
qi::uint_parser<uint8, 16, 1, 1> hexdigit;
ColorGrammar();
//! Rule for rgb(...)
qi::rule<ItType, Color(), qi::locals<float, float>, Skipper> rule_rgb;
//! Rule for rgba(...)
qi::rule<ItType, Color(), qi::locals<float, float, float>, Skipper> rule_rgba;
//! Mainrule
qi::rule<ItType, Color(), Skipper> rule_color;
};
Here is the cpp
ColorGrammar::ColorGrammar()
: ColorGrammar::base_type(rule_color, "color-grammar")
{
using namespace qi::labels;
using boost::phoenix::construct;
auto& _1 = qi::_1;
rule_rgb = '(' >> qi::float_[_a = _1] >> ',' >> qi::float_[_b = _1] >> ',' >> qi::float_[_val = phx::construct<Color>(_a, _b, _1)] >> ')';
rule_rgba = '(' >> qi::float_[_a = _1] >> ',' >> qi::float_[_b = _1] >> ',' >> qi::float_[_c = _1] >> ',' >> qi::float_[_val = phx::construct<Color>(_a, _b, _c, _1)] >> ')';
rule_color = (qi::lit("rgb") >> rule_rgb)
| (qi::lit("rgba") >> rule_rgba);
}
And the call:
Color out;
StringIterator begin = str.cbegin();
StringIterator end = str.cend();
bool result = qi::phrase_parse(begin, end, color_, chs::space, out);
I'm sure, it is only a little misstake, but I am not able to see it.
Maybe i watched too long at the source... can you see a misstake?

Answer 1

I can't see what's wrong: I've taken the effort to reconstruct your SSCCE.
http://liveworkspace.org/code/1pDtmn$1
In the process, it seems I must have removed the problem. I suggest you do the same.
Oh, and this is how I'd write this:
no more phoenix
no more constructors
no more qi::locals
no more needless copying
using expectation points
In short: no more fuss.
#include <boost/spirit/include/qi.hpp>
#include <boost/fusion/adapted/struct.hpp>
#include <cstdint>
namespace qi = boost::spirit::qi;
namespace chs = boost::spirit::ascii; //qi;
typedef std::string::const_iterator StringIterator;
struct Color
{
float r,g,b,a;
};
BOOST_FUSION_ADAPT_STRUCT(Color, (float, r)(float, g)(float, b)(float, a))
template <typename ItType, typename Skipper>
struct ColorGrammar : public qi::grammar<StringIterator, Color(), Skipper>
{
ColorGrammar()
: ColorGrammar::base_type(rule_color, "color-grammar")
{
using namespace qi;
rule_rgb = lit("rgb") >> '(' > float_ > ',' > float_ > ',' > float_ > attr(1.0f) > ')';
rule_rgba = lit("rgba") >> '(' > float_ > ',' > float_ > ',' > float_ > ',' > float_ > ')';
rule_color = rule_rgb | rule_rgba;
}
private:
qi::uint_parser<uint8_t, 10, 1, 3> number; // unused
qi::uint_parser<uint8_t, 16, 1, 1> hexdigit; // unused
qi::rule<ItType, Color(), Skipper> rule_rgb, rule_rgba, rule_color;
};
int main()
{
Color out;
std::string str = " rgb ( 0.3 , .4 , 0.5 )";
StringIterator begin = str.cbegin();
StringIterator end = str.cend();
ColorGrammar<StringIterator, chs::space_type> color_;
bool result = qi::phrase_parse(begin, end, color_, chs::space, out);
std::cout << std::boolalpha << result << '\n';
std::cout << "remains: '" << std::string(begin, end) << "'\n";
}
Live on http://liveworkspace.org/code/35htD$3