Re: [boost] [xpressive] capture float?

Subject: Re: [boost] [xpressive] capture float?
From: Greg Rubino (bibil.thaysose_at_[hidden])
Date: 2014-07-23 21:51:06

Hi Eric,

Thanks for getting back to me.  I'm pretty sure this must have something to
do with my Boost version (1.49.0).  Comments below.

On Wed, Jul 23, 2014 at 5:57 PM, Eric Niebler <eniebler_at_[hidden]> wrote:

> 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;
>
>
How did you get away with no #include<string>?

>         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)
>

I'm using c++03, so I have no auto :(

>             {
>                 std::cout << "(" << p.first << ", " << p.second << ")"
>                           << std::endl;
>             }
>         }
>     }
>
> Gives me this expected output:
>
>     (3.14, >)
>
>
When I compile with gcc 4.8 and Boost 1.55 at home I get the same result,
although my program looks more like this:

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

namespace xpr = boost::xpressive;

int main(int argc, char** argv) {

  typedef std::map<float, std::string> float_oper_map;
  typedef std::map<unsigned int, std::string> uint_oper_map;

  float_oper_map float_map;
  uint_oper_map uint_map;

  xpr::sregex relation = xpr::as_xpr("<=") | ">=" | "<" | ">";
  xpr::sregex float_restrict =
    !(xpr::s1 = relation) >>
    (xpr::s2 = (+xpr::_d >> '.' >> +xpr::_d))
    [
     xpr::ref(float_map)[xpr::as<float>(xpr::s2)] =
     xpr::as<std::string>(xpr::s1)
     ];
  xpr::sregex uint_restrict =
    !(xpr::s1 = relation) >>
    (xpr::s2 = +xpr::_d)
    [
     xpr::ref(uint_map)[xpr::as<unsigned int>(xpr::s2)] =
     xpr::as<std::string>(xpr::s1)
     ];
  xpr::sregex expression = uint_restrict | float_restrict;

  std::string float_str = ">3.14";
  std::string uint_str = ">3";

  if(xpr::regex_match(float_str, expression)) {
    BOOST_FOREACH(const float_oper_map::value_type& val, float_map) {
      std::cout << '(' << val.first << ',' << val.second << ')' <<
std::endl;
    }
  }
  if(xpr::regex_match(uint_str, expression)) {
    BOOST_FOREACH(const uint_oper_map::value_type& val, uint_map) {
      std::cout << '(' << val.first << ',' << val.second << ')' <<
std::endl;
    }
  }

  return 0;

}

// END

I'm going to try with Boost 1.49 and see if I get different results.  If
anything interesting happens, I'll get back on this thread.  I should
definitely be able to come up with a full repro tomorrow.

Thanks again!
Greg