[boost] Anyone interested in the following boost "utility" library

From: Tom Brinkman (reportbase_at_[hidden])
Date: 2005-03-18 23:39:13

How do you specify a string or a double, 
or an object as a template parameter?

c++ templates are a compile time construct, 
so the answer is that you can't, or at least 
not directly.   

However, with the use of existing 
boost libraries and a little 
compiler magic, you can actually specify 
a string, double or any object as a template
parameter.  

The following code is the proof of 
this concept.  I would like to gather feedback 
from the group and submit this as a boost 
utility library if there is sufficient interest.

//TODO
//1) compile the following code as main.cpp.
//2) run the application with 
three command line parameters.

#include <vector>
#include <string>
#include <iostream>
#include <boost/variant.hpp>

std::vector<boost::variant<int,
long,double,std::string> > resources;

template <bool>
struct resource{};

template <>
struct resource<false>
{
    template <typename INDEX, typename R>
    void operator()(INDEX index, R& out)
    {
        out = oost::get<R>
        (resources[index()]);
    }
};

template <>
struct resource<true>
{
    template <typename T, typename R>
      void operator()(T in, R& out)
    {
        out = in;
    }
};

template <typename T, typename R> inline
void get(R& out)
{
    resource<boost::is_convertible<
       T,R>::value> a;
    a(T(),out);
}

template <int T=-1>
struct resource_wrapper
{
    static const int value = T;
    int operator()(){return T;}
};

template <int T=0>
struct integer
{
    static const int value = T;
    operator int(){return T;}
};

typedef resource_wrapper<1> str1;
typedef resource_wrapper<2> str2;
typedef resource_wrapper<3> str3;
typedef resource_wrapper<4> columns;

template <typename STRING>
struct funct
{
    void operator()()
    {
       std::string str;
       get<STRING>(str);
       std::cout << str << std::endl;
    }
};

template <typename DOUBLE>
struct funct2
{
    void operator()()
    {
       double dbl;
       get<DOUBLE>(dbl);
       std::cout << dbl << std::endl;
    }
};

int main(int argc, char* argv[])
{
    resources.resize(100);
    resources[str1::value] = 
       std::string(argv[1]);
    resources[str2::value] = 	
       std::string(argv[2]);
    resources[str3::value] = 
std::string(argv[3]);
        resources[columns::value] = 6.33;

        funct<str1>()();	
        funct<str2>()();	
        funct<str3>()();	

        funct2<columns>()();
        funct2<integer<10> >()();

        return 0;
}

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