Phoenix function semantic action not compiling

Question

I wish to parse a string and ensure that it is lower case.

It has to be done at this stage because spirit builds tree out of it all.

so I have this rule

struct to_lower_object
{
    typedef char result_type;

    char operator()(char a) const
    {   
        return std::tolower(a);    
    }   
};


int main()
{

boost::phoenix::function<to_lower_object> lazy_lower;

qi::rule<std::string::iterator, char() >
    lower_char=(qi::char_-":")
    [
         qi::_val=lazy_lower(qi::_1);
    ];

qi::rule<std::string::iterator, std::string() >
    lower_string =
        +lower_char; 
:::

problem is that it doesn't compile, the error is massive also, to big to post.

Thanks

EDIT: I fixed the operator overload, that was my bad, but the problem persists. I beleive* it is to do with the placeholders

EDIT2: I have split the problem up to ensure that it is working on a char and not a series of them, but it still isn't working with the same reams of errors.

Answer 1

Well after much torment I finally got it working.

This:

struct to_lower_object
{
    typedef char result_type;

    char operator()(char a) const
    {   
        return std::tolower(a);    
    }   
};

Should have been:

struct to_lower_object
{
    template<typename Arg>
    struct result{
        typedef char type;
    };  

    template<typename Arg>
    char operator()(Arg arg1) const
    {   
        return std::tolower(a);    
    }   
};

Super. This apparently is because I was reading some old docs.

Answer 2

I'm pretty sure that the line qi::rule<std::string::iterator, std::string() > will never compile. Did you mean qi::rule<std::string::iterator, std::string > ?