Re: [boost] [xpressive] capture float?

Subject: Re: [boost] [xpressive] capture float?
From: Eric Niebler (eniebler_at_[hidden])
Date: 2014-07-23 19:57:25

On 7/23/2014 3:47 PM, Greg Rubino wrote:
> On Wed, Jul 23, 2014 at 4:07 PM, Greg Rubino wrote:
>> Hi all,
>>
>> I'm trying to capture a float with xpressive and put it into a local map.
>> As a simplified example, I tried just pushing the matched pattern to a
>> float and the result is always a float containing '0'.
>>
>>    namespace xpr = boost::xpressive;
>>
>>     std::map<float, std::string> l_floatOperMap;
>>
>>     xpr::sregex l_relation = xpr::as_xpr("<=") | ">=" | "<" | ">");
>>     l_floatRestriction =
>>         !(xpr::s1 = l_relation) >> (xpr::s2 = (+xpr::_d >> '.' >>
>> +xpr::_d))
>>        [xpr::ref(l_floatOperMap)[xpr::as<float>(xpr::s2)] =
>> xpr::as<std::string>(xpr::s1)];
>>
>>
>> However, when I go to print the contents of l_floatOperMap, it contains
>> only the tuple (0, "").  Is it something I'm doing wrong?  It seems like
>> this should work to me.
>>
>>
> I neglected to mention that I am actually doing the very same thing with
> uint32_t and it works fine.

Works for me. This program:

    #include <map>
    #include <iostream>
    #include <boost/xpressive/xpressive.hpp>
    #include <boost/xpressive/regex_actions.hpp>

    int main()
    {
        namespace xpr = boost::xpressive;

        std::map<float, std::string> l_floatOperMap;

        xpr::sregex l_relation = xpr::as_xpr("<=") | ">=" | "<" | ">";
        xpr::sregex l_floatRestriction =
            !(xpr::s1 = l_relation) >>
             (xpr::s2 = (+xpr::_d >> '.' >> +xpr::_d))
             [
                xpr::ref(l_floatOperMap)[xpr::as<float>(xpr::s2)] =
                   xpr::as<std::string>(xpr::s1)
             ];

        std::string str = ">3.14";

        if(xpr::regex_match(str, l_floatRestriction))
        {
            for(auto p : l_floatOperMap)
            {
                std::cout << "(" << p.first << ", " << p.second << ")"
                          << std::endl;
            }
        }
    }

Gives me this expected output:

    (3.14, >)

Maybe you could send a complete repro?

Thanks,
Eric