Follow-up to post: [Using \* Width & Precision Specifiers With boost::format](https://stackoverflow.com/questions/2978096/using-width-precision-specifiers-with-boostformat)

I'm trying to use `boost::function` to create a function that uses lambdas to format a string with `boost::format`. Ultimately what I'm trying to achieve is using width & precision specifiers for strings with format. `boost::format` does not support the use of the `*` width & precision specifiers, as indicated [in the docs](http://www.boost.org/doc/libs/1_43_0/libs/format/doc/format.html#printf_directives):

> 
> Width or precision set to asterisk (\*)
>  are used by printf to read this field
>  from an argument. e.g.
>  printf("%1$d:%2$.\*3$d:%4$.\*3$d\n",
>  hour, min, precision, sec); This class
>  does not support this mechanism for
>  now. so such precision or width fields
>  are quietly ignored by the parsing.
> 
> 
> 

so I'm trying to find other ways to accomplish the same goal. 

Here is what I have so far, which isn't working:

```
#include <string>
#include <boost\function.hpp>
#include <boost\lambda\lambda.hpp>
#include <iostream>
#include <boost\format.hpp>
#include <iomanip>
#include <boost\bind.hpp>

int main()
{
 using namespace boost::lambda;
 using namespace std;

 boost::function<std::string(int, std::string)> f =
  (boost::format("%s") % boost::io::group(setw(_1*2), setprecision(_2*2), _3)).str();

 std::string s = (boost::format("%s") % f(15, "Hello")).str();

    return 0;
}

```

This generates many compiler errors:

```
1>------ Build started: Project: hacks, Configuration: Debug x64 ------
1>Compiling...
1>main.cpp
1>.\main.cpp(15) : error C2872: '_1' : ambiguous symbol
1>        could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(69) : boost::lambda::placeholder1_type &boost::lambda::`anonymous-namespace'::_1'
1>        or       'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(43) : boost::arg<I> `anonymous-namespace'::_1'
1>        with
1>        [
1>            I=1
1>        ]
1>.\main.cpp(15) : error C2664: 'std::setw' : cannot convert parameter 1 from 'boost::lambda::placeholder1_type' to 'std::streamsize'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>.\main.cpp(15) : error C2872: '_2' : ambiguous symbol
1>        could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(70) : boost::lambda::placeholder2_type &boost::lambda::`anonymous-namespace'::_2'
1>        or       'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(44) : boost::arg<I> `anonymous-namespace'::_2'
1>        with
1>        [
1>            I=2
1>        ]
1>.\main.cpp(15) : error C2664: 'std::setprecision' : cannot convert parameter 1 from 'boost::lambda::placeholder2_type' to 'std::streamsize'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>.\main.cpp(15) : error C2872: '_3' : ambiguous symbol
1>        could be 'D:\Program Files (x86)\boost\boost_1_42\boost/lambda/core.hpp(71) : boost::lambda::placeholder3_type &boost::lambda::`anonymous-namespace'::_3'
1>        or       'D:\Program Files (x86)\boost\boost_1_42\boost/bind/placeholders.hpp(45) : boost::arg<I> `anonymous-namespace'::_3'
1>        with
1>        [
1>            I=3
1>        ]
1>.\main.cpp(15) : error C2660: 'boost::io::group' : function does not take 3 arguments
1>.\main.cpp(15) : error C2228: left of '.str' must have class/struct/union
1>Build log was saved at "file://c:\Users\john\Documents\Visual Studio 2005\Projects\hacks\x64\Debug\BuildLog.htm"
1>hacks - 7 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

```

My fundamental understanding of boost's lambdas and functions is probably lacking. How can I get this to work?