[Boost-users] [fusion] Accessing sequence elements at runtime

From: Christian Henning (chhenning_at_[hidden])
Date: 2007-03-26 15:47:07

Hi there, is it somehow possible to access a sequence element at
runtime? Just image you're reading some name value pairs from file and
you would like them to assign them to a fusion sequences. This way I
don't know they order the values are supplied. Is that possible?

For example take the following code:

#include <string>
#include <algorithm>
#include <functional>
#include <vector>

#include <boost/any.hpp>
#include <boost/bind.hpp>

#include <boost/fusion/sequence.hpp>

using namespace std;
using namespace boost;

struct A {};
struct B {};

struct info
{
   string name;
   any    value_type;
};

static info info_table[] =
{
   { "A_Value", any( A() ) },
   { "B_Value", any( B() ) }
};

string& get_name( info& i )
{
   return i.name;
}

typedef fusion::map< fusion::pair< A , int >
                   , fusion::pair< B , double >
                   > seq_type;

int _tmain(int argc, _TCHAR* argv[])
{
   // Image a file read has delivered the following name value pair.
   string name = "A_Value";
   int a_value = 12;

   // Find the type of the supplied name
   info* p = find_if( &info_table[0]
                     , &info_table[0] + 2
                     , bind( equal_to<string>()
                           , bind( &get_name, _1 )
                           , name ));

   seq_type seq;
   // How to add the value to the supplied name??
}

Christian